True Televisions have the CRT Tube !!
Welcome to the Obsolete Technology Tellye Web Museum. Here you will see a TV Museum showing many Old Tube Television sets
all with the CRT Tube, B/W ,color, Digital, and 100HZ Scan rate, Tubes technology. This is the opportunity on the WEB to see, one more time, what real technology WAS ! In the mean time watch some crappy lcd picture around shop centers (but don't buy them, or money lost, they're already broken when new) !!!

Richtige Fernseher haben Röhren!

Richtige Fernseher haben Röhren!

In Brief: On this site you will find pictures and information about some of the electronic, electrical and electrotechnical technology relics that the Frank Sharp Private museum has accumulated over the years .

Premise: There are lots of vintage electrical and electronic items that have not survived well or even completely disappeared and forgotten.

Or are not being collected nowadays in proportion to their significance or prevalence in their heyday, this is bad and the main part of the death land. The heavy, ugly sarcophagus; models with few endearing qualities, devices that have some over-riding disadvantage to ownership such as heavy weight,toxicity or inflated value when dismantled, tend to be under-represented by all but the most comprehensive collections and museums. They get relegated to the bottom of the wants list, derided as 'more trouble than they are worth', or just forgotten entirely. As a result, I started to notice gaps in the current representation of the history of electronic and electrical technology to the interested member of the public.

Following this idea around a bit, convinced me that a collection of the peculiar alone could not hope to survive on its own merits, but a museum that gave equal display space to the popular and the unpopular, would bring things to the attention of the average person that he has previously passed by or been shielded from. It's a matter of culture. From this, the Obsolete Technology Tellye Web Museum concept developed and all my other things too. It's an open platform for all electrical Electronic TV technology to have its few, but NOT last, moments of fame in a working, hand-on environment. We'll never own Colossus or Faraday's first transformer, but I can show things that you can't see at the Science Museum, and let you play with things that the Smithsonian can't allow people to touch, because my remit is different.

There was a society once that was the polar opposite of our disposable, junk society. A whole nation was built on the idea of placing quality before quantity in all things. The goal was not “more and newer,” but “better and higher" .This attitude was reflected not only in the manufacturing of material goods, but also in the realms of art and architecture, as well as in the social fabric of everyday life. The goal was for each new cohort of children to stand on a higher level than the preceding cohort: they were to be healthier, stronger, more intelligent, and more vibrant in every way.

The society that prioritized human, social and material quality is a Winner. Truly, it is the high point of all Western civilization. Consequently, its defeat meant the defeat of civilization itself.

Today, the West is headed for the abyss. For the ultimate fate of our disposable society is for that society itself to be disposed of. And this will happen sooner, rather than later.

OLD, but ORIGINAL, Well made, Funny, Not remotely controlled............. and not Made in CHINA.

How to use the site:

- If you landed here via any Search Engine, you will get what you searched for and you can search more using the search this blog feature provided by Google. You can visit more posts scrolling the left blog archive of all posts of the month/year,or you can click on the main photo-page to start from the main page. Doing so it starts from the most recent post to the older post simple clicking on the Older Post button on the bottom of each page after reading , post after post.

You can even visit all posts, time to time, when reaching the bottom end of each page and click on the Older Post button.

- If you arrived here at the main page via bookmark you can visit all the site scrolling the left blog archive of all posts of the month/year pointing were you want , or more simple You can even visit all blog posts, from newer to older, clicking at the end of each bottom page on the Older Post button.So you can see all the blog/site content surfing all pages in it.

- The search this blog feature provided by Google is a real search engine. If you're pointing particular things it will search IT for you; or you can place a brand name in the search query at your choice and visit all results page by page. It's useful since the content of the site is very large.

Note that if you don't find what you searched for, try it after a period of time; the site is a never ending job !

Every CRT Television saved let revive knowledge, thoughts, moments of the past life which will never return again.........

Many contemporary "televisions" (more correctly named as displays) would not have this level of staying power, many would ware out or require major services within just five years or less and of course, there is that perennial bug bear of planned obsolescence where components are deliberately designed to fail and, or manufactured with limited edition specificities..... and without considering........picture......sound........quality........

Saturday, August 27, 2011

The CUC series was replacing all earlier Grundig TV chassis types known as thyristors deflection based

- A completely NEW design of power supply was developed By GRUNDIG when designing the CUC720 CUC740 CHASSIS SERIES.

Based on TDA4600 (SIEMENS) was Universally used for very long time since the design Of the CHASSIS CUC720 is the father of all chassis design from 1981 to the end of GRUNDIG productions, employing a varyiety of versions type of the control IC (TDA460X) except for CHASSIS CUC2201 and CUC3400 and CUC3410 and CUC3510 which they're based on other technology.

SIEMENS TDA4600 Operation.* The TDA4601 device is a single in line, 9 pin chip. Its predecessor was the TDA4600device, the TDA4601 however has improved switching, better protection and cooler running.The (SIEMENS) TDA4601 power supply is a fairly standard parallel chopper switch mode type,which operates on the same basic principle as a line output stage. It is turned on and off by asquare wave drive pulse, when switched on energy is stored in the chopper transformerprimary winding in the form of a magnetic flux; when the chopper is turned off the magneticflux collapses, causing a large back emf to be produced. At the secondary side of the choppertransformer this is rectified and smoothed for H.T. supply purposes.The advantage of this type of supply is that the high chopping frequency (20 to 70 KHzaccording to load) allows the use of relatively small H.T. smoothing capacitors makingsmoothing easier. Also should the chopper device go short circuit there is no H.T. output.In order to start up the TDA4601 I.C. an initial supply of 9v is required at pin 9, this voltageis sourced via R818 and D805 from the AC side of the bridge rectifier D801, also pin 5requires a +Ve bias for the internal logic block. (On some sets pin 5 is used for standbyswitching). Once the power supply is up and running, the voltage on pin 9 is increased to 16vand maintained at this level by D807 and C820 acting as a half wave rectifier and smoothingcircuit.PIN DESCRIPTIONSPin 1 This is a 4v reference produced within the I.C.Pin 2 This pin detects the exact point at which energy stored in the chopper transformercollapses to zero via R824 and R825, and allows Q1 to deliver drive volts to thechopper transistor. It also opens the switch at pin 4 allowing the external capacitorC813 to charge from its external feed resistor R810.Pin 3 H.T. control/feedback via photo coupler D830.The voltage at this pin controls the on time of the chopper transistor and hence theoutput voltage. Normally it runs at Approximately 2v and regulates H.T. by sensing aproportion of the +4v reference at pin 1, offset by conduction of the photo couplerD830 which acts like a variable resistor. An increase in the conduction of transistorD830 and therefor a reduction of its resistance will cause a corresponding reductionof the positive voltage at Pin 3. A decrease in this voltage will result in a shorteron time for the chopper transistor and therefor a lowering of the output voltage andvice versa, oscillation frequency also varies according to load, the higher the load thelower the frequency etc. should the voltage at pin 3 exceed 2.3v an internal flipflop is triggered causing the chopper drive mark space ratio to extend to 244 (offtime) to 1 (on time), the chip is now in over volts trip condition.Pin 4 At this pin a sawtooth waveform is generated which simulates chopper current, it isproduced by a time constant network R810 and C813. C813 charges when thechopper is on and is discharged when the chopper is off, by an internal switchstrapping pin 4 to the internal +2v reference, see Fig 2.The amplitude of the ramp is proportional to chopper drive. In an overloadcondition it reaches 4v amplitude at which point chopper drive is reduced to amark-space ratio of 13 to 1, the chip is then in over current trip.The I.C. can easily withstand a short circuit on the H.T. rail and in such a case thepower supply simply squegs quietly. Pin 4 is protected by internal protectioncomponents which limit the maximum voltage at this pin to 6.5v.Should a fault occur in either of the time constant components, then the choppertransistor will probably be destroyed.Pin 5 This pin can be used for remote control on/off switching of the power supply, it isnormally held at about +7v and will cause the chip to enter standby mode if it fallsbelow 2v.Pin 6 Ground.Pin 7 Chopper switch off pin. This pin clamps the chopper drive voltage to 1.6v in order toswitch off the chopper.Pin 8 Chopper base current output drive pin.Pin 9 L.T. pin, approximately 9v under start-up conditions and 16v during normal running,Current consumption of the I.C. is typically 135mA. The voltage at this pin mustreach 6.7v in order for the chip to start-up.Semiconductor circuit for supplying power to electrical equipment, comprising a transformer having a primary winding connected, via a parallel connection of a collector-emitter path of a transistor with a first capacitor, to both outputs of a rectifier circuit supplied, in turn, by a line a-c voltage; said transistor having a base controlled via a second capacitor by an output of a control circuit acted upon, in turn by the rectified a-c line voltage as actual value and by a reference voltage; said transformer having a first secondary winding to which the electrical equipment to be supplied is connected; said transformer having a second secondary winding with one terminal thereof connected to the emitter of said transistor and the other terminal thereof connected to an anode of a first diode leading to said control circuit; said transformer having a third secondary winding with one terminal thereof connected, on the one hand, via a series connection of a third capacitor with a first resistance, to the other terminal of said third secondary winding and connected, on the other hand, to the emitter of said transistor, the collector of which is connected to said primary winding; a point between said third capacitor and said first resistance being connected to the cathode of a second diode; said control circuit having nine terminals including a first terminal delivering a reference voltage and connected, via a voltage divider formed of a third and fourth series-connected resistances, to the anode of said second diode; a second terminal of said control circuit serving for zero-crossing identification being connected via a fifth resistance to said cathode of said second diode; a third terminal of said control-circuit serving as actual value input being directly connected to a divider point of said voltage divider forming said connection of said first terminal of said control circuit to said anode of said second diode; a fourth terminal of said control circuit delivering a sawtooth voltage being connected via a sixth resistance to a terminal of said primary winding of said transformer facing away from said transistor; a fifth terminal of said control circuit serving as a protective input being connected, via a seventh resistance to the cathode of said first diode and, through the intermediary of said seventh resistance and an eighth resistance, to the cathode of a third diode having an anode connected to an input of said rectifier circuit; a sixth terminal of said control circuit carrying said reference potential and being connected via a fourth capacitor to said fourth terminal of said control circuit and via a fifth capacitor to the anode of said second diode; a seventh terminal of said control circuit establishing a potential for pulses controlling said transistor being connected directly and an eighth terminal of said control circuit effecting pulse control of the base of said transistor being connected through the intermediary of a ninth resistance to said first capacitor leading to the base of said transistor; and a ninth terminal of said control circuit serving as a power supply input of said control circuit being connected both to the cathode of said first diode as well as via the intermediary of a sixth capacitor to a terminal of said second secondary winding as well as to a terminal of said third secondary winding.

Description:

The invention relates to a blocking oscillator type switching power supply for supplying power to electrical equipment, wherein the primary winding of a transformer, in series with the emitter-collector path of a first bipolar transistor, is connected to a d-c voltage obtained by rectification of a line a-c voltage fed-in via two external supply terminals, and a secondary winding of the transformer is provided for supplying power to the electrical equipment, wherein, furthermore, the first bipolar transistor has a base controlled by the output of a control circuit which is acted upon in turn by the rectified a-c line voltage as actual value and by a set-point transmitter, and wherein a starting circuit for further control of the base of the first bipolar transistor is provided.
Such a blocking oscillator switching power supply is described in the German periodical, "Funkschau" (1975) No. 5, pages 40 to 44. It is well known that the purpose of such a circuit is to supply electronic equipment, for example, a television set, with stabilized and controlled supply voltages. Essential for such switching power supply is a power switching transistor i.e. a bipolar transistor with high switching speed and high reverse voltage. This transistor therefore constitutes an important component of the control element of the control circuit. Furthermore, a high operating frequency and a transformer intended for a high operating frequency are provided, because generally, a thorough separation of the equipment to be supplied from the supply naturally is desired. Such switching power supplies may be constructed either for synchronized or externally controlled operation or for non-synchronized or free-running operation. A blocking converter is understood to be a switching power supply in which power is delivered to the equipment to be supplied only if the switching transistor establishing the connection between the primary coil of the transformer and the rectified a-c voltage is cut off. The power delivered by the line rectifier to the primary coil of the transformer while the switching transistor is open, is interim-stored in the transformer and then delivered to the consumer on the secondary side of the transformer with the switching transistor cut off.
In the blocking converter described in the aforementioned reference in the literature, "Funkschau" (1975), No. 5, Pages 40 to 44, the power switching transistor is connected in the manner defined in the introduction to this application. In addition, a so-called starting circuit is provided. Because several diodes are generally provided in the overall circuit of a blocking oscillator according to the definition provided in the introduction hereto, it is necessary, in order not to damage these diodes, that due to the collector peak current in the case of a short circuit, no excessive stress of these diodes and possibly existing further sensitive circuit parts can occur. Considering the operation of a blocking oscillator, this means that, in the event of a short circuit, the number of collector current pulses per unit time must be reduced. For this purpose, a control and regulating circuit is provided. Simultaneously, a starting circuit must bring the blocking converter back to normal operation when the equipment is switched on, and after disturbances, for example, in the event of a short circuit. The starting circuit shown in the literature reference "Funkschau" on Page 42 thereof, differs to some extent already from the conventional d-c starting circuits. It is commonly known for all heretofore known blocking oscillator circuits, however, that a thyristor or an equivalent circuit replacing the thyristor is essential for the operation of the control circuit. It is accordingly an object of the invention to provide another starting circuit. It is a further object of the invention to provide a possible circuit for the control circuit which is particularly well suited for this purpose. It is yet another object of the invention to provide such a power supply which is assured of operation over the entire range of line voltages from 90 to 270 V a-c, while the secondary voltages and secondary load variations between no-load and short circuit are largely constant.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a blocking oscillator-type switching power supply for supplying power to electrical equipment wherein a primary winding of a transformer, in series with an emitter-collector path of a first bipolar transistor, is connected to a d-c voltage obtained by rectification of a line a-c voltage fed-in via two external supply terminals, a secondary winding of the transformer being connectible to the electrical equipment for supplying power thereto, the first bipolar transistor having a base controlled by the output of a control circuit acted upon, in turn, by the rectified a-c line voltage as actual value and by a set-point transmitter, and including a starting circuit for further control of the base of the first bipolar transistor, including a first diode in the starting circuit having an anode directly connected to one of the supply terminals supplied by the a-c line voltage and a cathode connected via a resistor to an input serving to supply power to the control circuit, the input being directly connected to a cathode of a second diode, the second diode having an anode connected to one terminal of another secondary winding of the transformer, the other secondary winding having another terminal connected to the emitter of the first bipolar transmitter.
In accordance with another feature of the invention, there is provided a second bipolar transistor having the same conduction type as that of the first bipolar transistor and connected in the starting circuit with the base thereof connected to a cathode of a semiconductor diode, the semiconductor diode having an anode connected to the emitter of the first bipolar transistor, the second bipolar transistor having a collector connected via a resistor to a cathode of the first diode in the starting circuit, and having an emitter connected to the input serving to supply power to the control circuit and also connected to the cathode of the second diode which is connected to the other secondary winding of the transformer.
In accordance with a further feature of the invention, the base of the second bipolar transistor is connected to a resistor and via the latter to one pole of a first capacitor, the anode of the first diode being connected to the other pole of the first capacitor. In accordance with an added feature of the invention, the input serving to supply power to the control circuit is connected via a second capacitor to an output of a line rectifier, the output of the line rectifier being directly connected to the emitter of the first bipolar transistor.
In accordance with an additional feature of the invention, the other secondary winding is connected at one end to the emitter of the first bipolar transistor and to a pole of a third capacitor, the third capacitor having another pole connected, on the one hand, via a resistor, to the other end of the other secondary winding and, on the other hand, to a cathode of a third diode, the third diode having an anode connected via a potentiometer to an actual value input of the control circuit and, via a fourth capacitor, to the emitter of the first bipolar transistor.
In accordance with yet another feature of the invention, the control circuit has a control output connected via a fifth capacitor to the base of the first bipolar transistor for conducting to the latter control pulses generated in the control circuit.
In accordance with a concomitant feature of the invention, there is provided a sixth capacitor shunting the emitter-collector path of the first transistor.
Other features which are considered as characteristic for the invention are set forth in the appended claim.
Although the invention is illustrated and described herein as embodied in a blocking oscillator type switching power supply, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

Note on the upper right chassis the Ensemble / Stereo bandwidth enhancer unit.

This version Incorporates a Stereo band expansion Unit fitted on the right bottom side of the cabinet.

It combines circuits to feature the Stereo sound expansion:29502.006.01
A system and method for enhancing the stereo sound effect produced by speaker systems having two or more speakers fed by two or more channels or audio, respectively. Second-order high pass filtering is applied to first and second audio signals of a stereo signal. A phase shift of approximately 180 degrees is applied to the resulting signals. A mixer mixes the processed first audio signal with the original second audio signal and mixes the processed second audio signal with the original first audio signal, whereby an expanded stereo sound field effect is created.

Stereo separation is the ability of an audio system to reproduce the spatial location information of sound sources in an audio recording. During stereo recording, two or more microphones, in different locations, are typically used to record an acoustic source. The time delays and pressure differences between the audio signals from the microphones provide spatial information. The spatial information allows the listener to interpolate the location of the various sound sources in the recording. By contrast, a monophonic sound recording may contain the same detail of the recorded source, but will not contain the spatial information of stereophonic sound.

Various design factors may have a negative affect on stereo separation. For example, audio systems which have the right and left stereo speaker drivers in close proximity to each other can suffer from poor channel separation, which reduces the stereo sound field effect, yielding a sound that is more monophonic than stereophonic. Other factors that can negatively affect stereo separation include, but are not limited to, the physical design of the speaker enclosure, speaker placement within the enclosure, and sound processing techniques, including bass enhancement circuits or algorithms.

In audio systems that include two speaker drivers and a subwoofer, driving the speakers out of phase with respect to each other can be used to enhance the stereo sound field effect. This technique is generally disadvantageous, however, particularly in audio systems containing two speaker drivers without a subwoofer, because it can cause phase-related distortion of the low-frequency content due to the generally monophonic nature of such content; because the low-frequency signal is substantially the same in both the left and right channels, running the left and right speakers out of phase causes cancellation of desirable low frequencies.

Various electrical circuits have been provided for enhancing the stereo sound field, but these typically utilize complex circuitry and speaker driver configurations to create the effect. For example, U.S. Pat. No. 5,870,484 to Greenberger teaches a sound reproduction system having an array of loudspeaker transducer elements that operate in combination with signal processing circuitry to control the radiation pattern of sound radiating from the system. Signals fed to the system are manipulated by the signal processing circuitry so that the signals are each radiated in their desired directions, thereby improving spatial separation. Such approaches, however, are complex and expensive to implement, and are inappropriate for stereo systems containing a small number of loudspeaker transducer elements.

It is therefore an object of the invention to provide an improved system and method for enhancing the stereo sound field in speaker systems.

It is one object of the invention to provide a system and method for providing enhanced stereo sound field which overcomes one or more of the limitations of the prior art.

It is a further object of the invention to provide an enhanced stereo sound effect in audio systems that include two or more speaker drivers but which do not include a subwoofer.

It is a further object of the invention to provide a system and method for enhancing the stereo sound effect without sacrificing low frequency content.

In one embodiment, the invention provides a system and method for enhancing the stereo sound effect produced by speaker systems having two or more speakers fed by two or more channels or audio, respectively. Second-order high pass filtering is applied to first and second audio signals of a stereo signal. A phase shift of approximately 180 degrees is applied to the resulting signals. A mixer mixes the processed first audio signal with the original second audio signal and mixes the processed second audio signal with the original first audio signal, whereby an expanded stereo sound field effect is created.

The disclosed system and method can be used in any audio system and is particularly useful when the audio system contains two or more speaker drivers without a subwoofer. The system and method improves the stereo field without sacrificing low frequency content.

TDA3561A (PHILIPS)

Luminance+Chrominance+RGB MATRIX
PAL decoder TDA3561A

GENERAL DESCRIPTION

The TDA3561A is a decoder for the PAL colour television standard. It combines all functions required for the identification
and demodulation of PAL signals.

Furthermore it contains a luminance amplifier, an RGB-matrix and amplifier. These
amplifiers supply output signals up to 5 V peak-to-peak (picture information) enabling direct drive of the discrete output
stages.
The circuit also contains separate inputs for data insertion, analogue as well as digital, which can be used for text display systems (e.g. (Teletext/broadcast antiope), channel number display, etc. Additional to the TDA3560, the
circuit includes the following features:

· The peak white limiter is only active during the time that the 9,3 V level at the output is exceeded.
The start of the
limiting function is delayed by one line period. This avoids peak white limiting by test patterns which have abrupt transitions from colour to white signals.

· The brightness control is obtained by inserting a variable pulse in the luminance channel. Therefore the ratio of brightness variation and signal amplitude at the three outputs will be identical and independent of the difference in gain of the three channels. Thus discolouring due to adjustment of contrast and brightness is avoided.

· Improved suppression of the internal RGB signals when the device is switched to external signals, and vice versa.

· Non-synchronized external RGB signals do not disturb the black level of the internal signals.

DESCRIPTION
The TDA2030 is a monolithic integrated circuit in
Pentawatt[ package, intended for use as a low
frequency class AB amplifier. Typically it provides
14W output power (d = 0.5%) at 14V/4W; at ± 14V
or 28V, the guaranteed output power is 12W on a
4W load and 8W on a 8W (DIN45500).
TheTDA2030 provideshigh outputcurrentand has
very low harmonic and cross-over distortion.
Further the device incorporates an original (and
patented) short circuit protection system comprising
an arrangement for automatically limiting the
dissipated power so as to keep the working point
of the output transistors within their safe operating
area.A conventional thermal shut-down system is
also included.

SHORT CIRCUIT PROTECTION
TheTDA2030hasan original circuit whichlimits the
current of the output transistors. Fig. 18 shows that
the maximum output current is a function of the
collector emitter voltage; hence the output transistors
work within their safe operating area (Fig. 2).
This function can thereforebe consideredas being
peak power limiting rather than simple current limiting.
It reduces the possibility that the device gets damaged
during an accidental short circuit from AC
output to ground.

THERMAL SHUT-DOWN
The presence of a thermal limiting circuit offers the
following advantages:
1. An overload on the output (even if it is permanent),
or an abovelimit ambienttemperaturecan
be easily supported since the Tj cannot be
higher than 150°C.
2. The heatsink can have a smaller factor of safety
compared with that of a conventional circuit.
There is no possibility of device damage due to
high junction temperature.If for any reason, the
junction temperatureincreasesup to 150°C, the
thermal shut-down simply reduces the power
dissipation at the current consumption.
The maximum allowable power dissipation depends
upon the size of the external heatsink (i.e. its
thermal resistance); fig. 22 shows this dissipable
power as a function of ambient temperature for
different thermal resistance.

- Stereo Sound Decoder 29504-002.001 TDA2795 + TDA1195 + TDA4942.

- Sound Amplifier unit 29504-004.12 TDA2030 (see above)

GRUNDIG SUPER COLOR B7502 SERIE 3022 SUPERSOUND CHASSIS CUC740 Remote control television with external data bus connection,Remote Control With MOS IC's For TV Sets: THE GRUNDIG AV FEATURE CONNECTOR TECHNOLOGY:A television receiver is provided for use as a picture display terminal for electronic peripheral equipment, where a control system with a data-bus is built into the television receiver for multitude of commands and in which the television receiver is intended to be used in addition to the normal direct reception of televised pictures for other possible applications. The television receiver can serve as a monitor for a picture tape recorder, which is equipped for recording independently of the television receiver. A complete television receiving set is provided with automatic transmitter seeking mechanism and electronic channel storage.

1. A system for the use of a television receiver for external control of electronic peripheral devices, said television being of the type including a built-in integrated circuit remote control receiver, said remote control receiver being divided into two sections, one section being allocated to the remote control of the receiving and reproduction sections of the television receiver and the other section being allocated to a databus having nothing to do with the television receiver receiving and reproduction sections; an output terminal of said databus comprising an adaptor connector between said television receiver and an external peripheral device; a peripheral device external to the television receiver; cable means connecting the output of said databus with said peripheral device; and a decoder interposed between said databus output terminal and peripheral device for converting data from said databus into a form suitable for controlling functions of said peripheral device.

2. A television receiver as a picture terminal according to claim 1, in which said external coupling includes a connecting cable between the external connections of the television set and the peripheral device forming a unitary unit together with a decoder which transforms the data from the data collector into a code which directly controls the functions of the peripheral device.

3. A television receiver as a picture terminal according to claim 1 or 2, in which the peripheral device is a picture taping device which operates for recording independently from the television set which acts as a monitor.

4. A television receiver as a picture terminal according to claim 1, in which the functions controlled by said first commands include the on-off switching, picture, sound and channel selection of the television receiver and the functions controlled by said second commands include electronic program storage and changeover functions.

Description:

BACKGROUND OF THE INVENTION
Integrated circuits are presently known in the art for the convenient operation of television receivers, whereby the functions of on-off switching, channel selection, picture (video) and sound (audio) can be remotely controlled by the received telecontrol signal. In particular, the following function can be operated by such a system: Switching on and off of the equipment, calling for different program channels, variations and basic adjustments of sound level, brightness and color saturation, silencing of the sound as well as inserting of time references. With a known and presently available operating system up to 16 channels can be installed, so that it is possible, to select directly that number of programs and to tune the receiver to the appropriate channel.
Television receivers available today in many designs provide for up to 30 remotely controlled channels or channels controlled by the received signal (tele-signal) to properly operate. Additionally, infrared control is also becoming popular. These controls provide commands by means of a databus so that the operation of the various functions is possible with the provision of additional commands.
It is further known to equip peripheral equipment such as video tape recorders with a so-called electronic-tap-key rather than keys with a long throw so that all parts which are susceptable to mechanical wear are eliminated and replaced by digital controls.
It has become of interest to connect the peripheral equipment such as the video tape recorder to the television receiver so that both can be conveniently operated. With the development of new concepts simplification of design becomes critical for ease of operation and reduction of expense.
SUMMARY OF THE INVENTION
A .television receiver as a picture display terminal for electronic peripheral devices wherein a remote control system with a data collector is installed for receiving a plurality of commands and in which only a portion of the commands is used for the remote control functions of the receiving and display portions of the television set, while another portion of the commands is used for adjusting the functions of an electronic peripheral device which may be coupled with a television set, and that the data collector is electrically coupled by means of an external coupling of the television set with the corresponding stages of the peripheral device.
BRIEF DESCRIPTION OF THE DRAWING
The FIGURE is a diagrammatic showing of a television receiver and electronic periphery device incorporating the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
A television receiver and electronic peripheral device incorporating the invention are shown in the FIGURE. The television receiver 10 can be used as a picture display terminal for peripheral device 12. This provides the advantage, that by means of a single tele-control signal, the control of functions of the receiving and displaying sections of the television receiver can be accomplished as wel.l as the control functions of the peripheral equipment 12, which is connected to the receiver. The peripheral device does not require a separate tele-control system since that which is already installed in the television receiver can be used. To accomplish this, portion A of the available commands A, B of the tele-control system 11 are used for the function of the television receiver 10. The remaining portion B of the available commands A, B, which is made available at databus or data collector 14 is used for the control of functions of the peripheral equipment. The databus, which is coordinated with the peripheral equipment, and which is built into the tele-control system of the television receiver, is connected electrically to external terminal 16 of the television receiver. The external terminals at television receivers and peripheral equipment are relatively inexpensive.
The primary expenses result from the necessary cable connections between the external terminals of the television receiver and the peripheral equipment, as well as the auxiliary apparatus, such as decoder 18, which decodes the data from the databus 14 and prepares it for the peripheral equipment. These expenses are reduced by simplified design, in which the connecting cables 20 and 22 together with the auxiliary apparatus or decoder 18 are combined in one component or building block. This building block can be offered as an accessory to the user of television receivers with peripheral equipment.
The invention can be used with especial advantage in connecting a television receiver with a picture tape recorder as a peripheral equipment. The picture tape recorder is equipped preferably for recording independently from the television receiver, so that the latter serves as a monitor only. With such a switching combination it is possible, for example, to accomplish this with a single control system, and by the help of a tele-control system, which is built into the television receiver, to operate the channel selection and drive mechanism control, the control for an electronic switch clock and programming of the switch commands of the picture tape recorder as well as the control of the function of the receiving and displaying unit of the receiver. In this way it is possible to use the tele-control of a television receiver additionally for the tele-control of the picture tape recorder without substantial higher expenses.

In
a teletext decoder circuit the character generator supplies picture
elements at a rate of nominally approximately 6 MHz under the control of
display pulses occurring at the same rate. These display pulses are
derived from reference clock pulses which occur at a rate which is not a
rational multiple of 6 MHz. The character generator comprises a
generator circuit which receives the reference clock pulses and selects,
from each series of N reference clock pulses, as many pulses as
correspond to the number of horizontal picture elements constituting a
character, while the time interval of N reference clock pulses
corresponds to the desired width of the characters to be displayed. The
character generator supplies picture elements of distinct length,
while the length of a picture element is dependent on the ordinal
number of this picture element in the character.

1.
A receiver for television signal s including a teletext decoder
circuit for decoding teletext signals constituted by character codes
which are transmitted in the television signal, and comprising:
a video input circuit receiving the television signal and converting it into a serial data flow;
an
acquisition circuit for receiving the serial data flow supplied by
the video input circuit and selecting that part therefrom which
corresponds to the teletext page described by the viewer;
a character generator comprising:
a
memory medium addressed by the character codes which together
represent the teletext page desired by the user and which in response to
each character code successively supply m2 series of m1
simultaneously occurring character picture element codes each
indicating wether a corresponding picture element of the character must
be displayed in the foreground colour or in the background colour;
a generator circuit receiving a series of reference clock pulses and deriving display clock pulses therefrom;
a converter circuit receiving each series of m1 simultaneously occurring character picture element codes as well as the display clock pulses for supplying the m1 character picture element codes of a series one after the other and at the display clock pulse rate;
a
display control circuit receiving the serial character picture
element codes and converting each into an R, a G and a B signal for the
relevant picture element of the character to be displayed;
characterized in that
the
generator circuit is adapted to partition the series of reference
clock pulses applied thereto into groups of N reference clock pulses
each, in which N reference clock pulse periods correspond to the desired
width of a character to be displayed, and to select from each such
group m1 clock pulse to function as display clock pulses;
the
converter circuit is adapted to supply each character picture element
code during a period which is dependent on the ordinal number of the
character picture element code in the series of m1 character picture element codes.
2. A character generator for use in a receiver teletext claim 1, comprising:
a memory medium which is addressable by character codes and successively applies m2 series of m1
simultaneously occurring character picture element codes in response
to a character code applied as an address thereto, each character
picture element code indicating whether a corresponding picture element
of the character must be displayed in the foreground colour or in the
background colour;
a generator circuit receiving a series of reference clock pulses and deriving display clock pulses therefrom;
a converter circuit receiving each series of m1 simultaneously occurring character picture element codes and the display clock pulses for supplying the m1 character picture element codes of the series one after the other at the display clock pulse rate;
a
display control circuit receiving the serial character picture
element codes and converting each into an R, a G and a B signal for the
relevant picture element of the character to be displayed;
characterized in that
the generator circuit is adapted to
partition the series of reference clock pulses applied thereto into
groups of N reference clock pulses each, in which N reference clock
pulse periods correspond to the desired width of a character to be
displayed, and to select from each such group m1 clock pulses to function as display clock pulses;
the
converter circuit is adapted to supply each character picture element
code during a period which is dependent on the ordinal number of the
character picture element code in the series of m1 character picture element codes.

Description:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The
invention generally relates to receivers for television signals and
more particularly to receivers including teletext decoders for use in a
teletext transmission system.
2. Description of the Prior Art
As
is generally known, in a teletext transmission system, a number of
pages is transmitted from a transmitter to the receiver in a
predetermined cyclic sequence. Such a page comprises a plurality of
lines and each line comprises a plurality of alphanumerical characters. A
character code is assigned to each of these characters and all
character codes are transmitted in those (or a number of those)
television lines which are not used for the transmission of video
signals. These television lines are usually referred to as data lines.
Nowadays
the teletext transmission system is based on the standard known as
"World System Teletext", abbreviates WST. According to this standard
each page has 24 lines and each line comprises 40 characters.
Furthermore each data line comprises, inter alia, a line number (in a
binary form) and the 40 character codes of the 40 characters of that
line.
A receiver which is suitable for use in such a teletext
transmission system includes a teletext decoder enabling a user to
select a predetermined page for display on a screen. As is indicated in,
for example, Reference 1, a teletext decoder comprises, inter alia, a
video input circuit (VIP) which receives the received television
signal and converts it into a serial data flow. This flow is
subsequently applied to an acquisition circuit which selects those
data which are required for building up the page desired by the user.
The 40 character codes of each teletext line are stored in a page
memory which at a given moment thus comprises all character codes of
the desired page. These character codes are subsequently applied one
after the other and line by line to a character generator which
supplies such output signals that the said characters become visible
when signals are applied to a display.
For the purpose of display each character is considered as a matrix of m 1 ×m 2
picture elements which are displayed row by row on the screen. Each
picture element corresponds to a line section having a predetermined
length (measured with respect to time); for example, qμsec. Since each
line of a page comprises 40 characters and each character has a width
of m 1 qμsec, each line has a length of 40 m 1
μsec. In practice a length of approximately 36 to 44 μsec appears to
be a good choice. In the teletext decoder described in Reference 1
line length of 40 μsec and a character width of 1 μsec at m 1 =6 have been chosen.
The
central part of the character generator is constituted by a memory
which is sub-divided into a number of submemories, for example, one for
each character. Each sub-memory then comprises m 1 ×m 2
memory locations each corresponding to a picture element and the
contents of each memory location define whether the relevant picture
element must be displayed in the so-called foreground colour or in the
so-called background colour. The contents of such a code memory
location will be referred to as character picture element code. This
memory is each time addressed by a character code and a row code. The
character code selects the sub-memory and the row code selects the row
of m 1 memory elements whose contents are desired. The memory thus supplies groups of m
simultaneously occurring character picture element codes which are
applied to a converter circuit. This converter circuit usually includes a
buffer circuit for temporarily storing the m 1
substantially presented character picture element codes. It is
controlled by display clock pulses occurring at a given rate and being
supplied by a generator circuit. It also supplies the m 1
character picture element codes, which are stored in the buffer
circuit, one after the other and at a rate of the display clock
pulses. The serial character picture element codes thus obtained are
applied to a display control circuit converting each character picture
element code into an R, a G and a B signal value for the relevant
picture element, which signal values are applied to the display device
(for example, display tube).
The frequency f d at
which the display clock pulses occur directly determines the length
of a picture element and hence the character width. In the
above-mentioned case in which m 1 =6 and in which a character width of 1 μsec is chosen, this means that f d
=6 MHz. A change in the rate of the display clock pulses involves a
change in the length of a line of the page to be displayed (now 40
μsec). In practice a small deviation of, for example, not more than 5%
appears to be acceptable. For generating the display clock pulses the
generator circuit receives reference clock pulses. In the decoder
circuit described in Reference 1 these reference clock pulses are also
supplied at a rate of 6 MHz, more specifically by an oscillator
specially provided for this purpose.
OBJECT AND SUMMARY OF THE INVENTION
A
particular object of the invention is to provide a teletext decoder
circuit which does not include a separate 6 MHz oscillator but in which
for other reasons clock pulses, which are already present in the
television receiver, can be used as reference clock pulses, which
reference clock pulses generally do not occur at a rate which is a
rational multiple of the rate at which the display clock pulses must
occur.
According to the invention,
the generator
circuit is adapted to partition the series of reference clock pulses
applied thereto into groups of N reference clock pulses each, in which N
clock pulse periods correspond to the desired width of a character to
be displayed, and to select of each such group m 1 clockpulses to function as display clock pulses;
the
converter circuit is adapted to supply each character picture element
code during a period which is dependent on the ordinal number of the
character picture element code in the series of m 1 character picture element codes.
The
invention has resulted from research into teletext decoder circuits
for use in the field of digital video signal processing in which a 13.5
MHz clock generator is provided for sampling the video signal. The
13.5 MHz clock pulses supplied by this clock generator are now used as
reference clock pulses. The generator circuit partitions these
reference clock pulses into groups of N clock pulses periods each. The
width of such a group is equal to the desired character width. Since a
character comprises rows of m 1 picture elements, m 1
reference clock pulses are selected from such a group which clock
pulses are distributed over this group as regularly as possible. Since
the mutual distance between the display clock pulses thus obtained is
not constantly the same, further measures will have to be taken to
prevent undesired gaps from occurring between successive picture
elements when a character is displayed. Since the length of a picture
element is determined by the period during which the converter circuit
supplies a given character picture element code, this period has been
rendered dependent on the ordinal number of the character picture
element code in the series of m 1 character picture element codes.
REFERENCES
1. Computer-controlled teletext, J. R. Kinghorn; Electronic Components and Applications, Vol. 6, No. 1, 1984, pages 15-29.
2.
Video and associated systems, Bipolar, MOS; Types MAB 8031 AH to TDA
1521: Philips' Data Handbook, Integrated circuits, Book ICO2a 1986,
pages 374,375.
3. Bipolar IC's for video equipment; Philips' Data Handbook, Integrated Circuits Part 2, January 1983.
4.
IC' for digital systems in radio, audio and video equipment, Philips'
Data Handbook, Integrated Circuits Part 3, September 1982.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows the general structure of a television receiver including a teletext decoder circuit;
FIG. 2 shows different matrices of picture elements constituting a character;
FIG. 3 shows diagrammatically the general structure of a character generator;
FIG.
4 shows an embodiment of a converter circuit and a generator circuit
for use in the character generator shown in FIG. 3, and
FIG. 5 shows some time diagrams to explain its operation;
FIG.
6 shows another embodiment of a converter circuit and a generator
circuit for use in the character generator shown in FIG. 3, and
FIG. 7 shows some time diagrams to explain its operation;
FIG. 8 shows a modification of the converter circuit shown in FIG. 6, adapted to round the characters.
EXPLANATION OF THE INVENTION
General structure of a TV receiver
FIG. 1 shows diagrammatically
the general structure of a colour television receiver. It has an
antenna input 1 connected to an antenna 2 receiving a television signal
modulated on a high-frequency carrier, which signal is processed in a
plurality of processing circuits. More particularly, it is applied to
a tuning circuit 23 (tuner or channel selector). This circuit
receives a band selection voltage V B in order to enable
the receiver to be tuned to a frequency within one of the frequency
bands VHF1, VHF2, UHF, etc. The tuning circuit also receives a tuning
voltage V T with which the receiver is tuned to the desired frequency within the selected frequency band.
This tuning circuit 3 supplies an oscillator signal having a frequency of f OSC
on the one hand and an intermediate frequency video signal IF on the
other hand. The latter signal is applied to an intermediate frequency
amplification and demodulation circuit 4 supplying a baseband
composite video signal CVBS. The Philips IC TDA 2540 described in
Reference 3 can be used for this circuit 4.
The signal CVBS
thus obtained is also applied to a colour decoder circuit 5. this
circuit supplies the three primary colour signals R', G' and B' which
in their turn are applied via an amplifier circuit 6 to a display
device 7 in the form of a display tube for the display of broadcasts
on a display screen 8. In the colour decoder circuit 5 colour
saturation, contrast and brightness are influenced by means of control
signals ANL. The circuit also receives an additional set of primary
colour signals R, G and B and a switching signal BLK (blanking) with
which the primary colour signals R', G' and B' can be replaced by the
signals R, G and B of the additional set of primary colour signals. A
Philips IC of the TDA 356X family described in Reference 3 can be used
for this circuit 5.
The video signal CVBS is also applied to a
teletext decoder circuit 9. This circuit comprises a video input
circuit 91 which receives the video signal CVBS and converts it into a
serial data flow. This flow is applied to a circuit 92 which will be
referred to as teletext acquisition and control circuit (abbreviated
TAC circuit). This circuit selects that part of the data applied
thereto which corresponds to the teletext page desired by the viewer.
The character codes defined by these data are stored in a memory 93
which is generally referred to as page memory and are applied from
this memory to a character generator 94 supplying an R, a G and a B
signal for each picture element of the screen 8. It is to be noted
that this character generator 94 also supplies the switching signal
BLK in this embodiment. As is shown in the Figure, the teletext
acquisition and control circuit 92, the page memory 93 and the
character generator 94 are controlled by a control circuit 95 which
receives reference clock pulses with a frequency f o from a
reference clock oscillator 10. The control circuit 95 has such a
structure that it supplies the same reference clock pulses from its
output 951 with a phase which may be slightly shifted with respect to
the reference clock pulses supplied by the clock pulse oscillator 10
itself. The reference clock pulses occurring at this output 951 will be
denoted by TR. The
Philips IC SAA 5030 may be used as video input circuits 91, the
Philips IC SAA 5040 may be used as teletext acquisition and control
circuit, a 1K8 RAM may be used as page memory, a modified version of
the Philips IC SAA 5050 may be used as character generator 94 and a
modified version of the Philips IC SAA 5020 may be used as control
circuit 95, the obvious modification being a result of the fact that
this IC is originally intended to receive reference clock pulses at a
rate of 6 MHz for which 13.5 MHz has now been taken.
The
acquisition and control circuit 92 is also connected to a bus system
11. A control circuit 12 in the form of a microcomputer, an interface
circuit 13 and a non-volatile memory medium 14 are also connected to
this system. The interface circuit 13 supplies the said band selection
voltage V B , the tuning voltage V T and the
control signals ANL for controlling the analog functions of contrast,
brightness and colour saturation. It receives an oscillator signal at
the frequency f' OSC which is derived by means of a
frequency divider 15, a dividing factor of which is 256, from the
oscillator signal at the frequency f OSC which is supplied
by the tuning circuit 3. Tuning circuit 3, frequency divider 15 and
interface circuit 13 combined constitute a frequency synthesis circuit.
The Philips IC SAB 3035 known under the name of CITAC (Computer
Interface for Tuning and Analog Control) and described in Reference 4
can be used as interface circuit 13. A specimen from the MAB 84XX
family, manufactured by Philips, can be used as a microcomputer.
The
memory medium 14 is used, for example, for storing tuning data of a
plurality of preselected transmitter stations (or programs). When such
tuning data are applied to the interface circuit 13 under the control
of the microcomputer 12, this circuit supplies a given band selection
voltage V B and a given tuning voltage V T so that the receiver is tuned to the desired transmitter.
For
operating this television receiver an operating system is provided in
the form of a remote control system comprising a hand-held apparatus
16 and a local receiver 17. This receiver 17 has an output which is
connected to an input (usually the "interrupt" input) of the
microcomputer 12. It may be constituted by the Philips IC TDB 2033
described in Reference 4 and is then intended for receiving infrared
signals which are transmitted by the hand-held apparatus 16.
The
hand-held apparatus 16 comprises an operating panel 161 with a
plurality of figure keys denoted by the FIGS. 0 to 9 inclusive, a colour
saturation key SAT, a brightness key BRI, a volume key VOL, and a
teletext key TXT. These keys are coupled to a transmitter circuit 162
for which, for example, the Philips IC SAA 3004, which has extensively
been described in Reference 4, can be used. When a key is depressed, a
code which is specific of that key is generated by the transmitter
circuit 162, which code is transferred via an infrared carrier to the
local receiver 17, demodulated in this receiver and subsequently
presented to the microcomputer 12. This microcomputer thus receives
operating instructions and activates, via the bus system 11, one of
the circuits connected thereto. It is to be noted that an operating
instruction may be a single instruction, that is to say, it is complete
after depressing only one key. It may also be multiple, that is to
say, it is not complete until two or more keys have been depressed.
This situation occurs, for example, when the receiver is operating in
the teletext mode. Operation of figure keys then only yields a
complete operating instruction when, for example, three figure keys
have been depressed. As is known, such a combination results in the
page number of the desired teletext page.
The character generator
As already stated, a character is a matrix comprising m 2 rows of m 1
picture elements each. Each picture element corresponds to a line
section of a predetermined length (measured with respect to time); for
example, q/μsec. Such a matrix is indicated at A in FIG. 2 for m 1 =6 and m 2
=10. More particularly this is the matrix of a dummy character. The
character for the letter A is indicated at B in the same FIG. 2. It is
to be noted that the forty characters constituting a line of teletext
page are contiguous to one another without any interspace. The sixth
column of the matrix then ensures the required spacing between the
successive letters and figures.
FIG. 3 shows diagrammatically
the general structure of the character generator described in Reference 2
and adapted to supply a set of R, G and B signals for each picture
element of the character. This character generator comprises a buffer
940 which receives the character codes from memory 93 (see FIG. 1).
These character codes address a sub-memory in a memory medium 941, which
sub-memory consists of m 1 ×m 2 memory elements each comprising a character picture element code. Each m 1 ×m 2 character
picture element code corresponds to a picture element of the
character and defines, as already stated, whether the relevation
picture element must be displayed in the so-called foreground colour
or in the so-called background colour. Such a character picture
element code has the logic value "0" or "1". A "0" means that the
corresponding picture element must be displayed in the background
colour (for example, white). The "1" means that the corresponding
picture element must be displayed in the foreground colour (for
example, black or blue). At C in FIG. 2 there is indicated, the
contents of the sub-memory for the character shown at B in FIG. 2.
The
addressed sub-memory is read now by row under the control of a
character row signal LOSE. More particularly, all first rows are read
of the sub-memories of the forty characters of a teletext line,
subsequently all second rows are read, then all third rows are read
and so forth until finally all tenth rows are read.
The six
character element codes of a row will hereinafter be referred to as
CH(1), CH(2), . . . CH(6). They are made available in parallel by the
memory medium 941 and are applied to a converter circuit 942 operating
as a parallel-series converter. In addition to the six character
picture element codes it receives display clock pulses DCL and applies
these six character picture element codes one by one at the rate of
the display clock pulses to a display control circuit 943 which
converts each character picture element code into a set of R, G, B
signals.
The display clock pulses DCL and the character row
signal LOSE are supplied in known manner (see Reference 2, page 391) by
a generator circuit 944 which receives the reference clock pulses TR
from the control circuit 95 (see FIG. 1), which reference clock pulses
have a rate f 0 . In the character generator described in Reference 2, page 391, f 0
is 6 MHz and the display clock pulses DCL occur at the same rate. The
converter circuit thus supplies the separate character picture
element codes at a rate of 6 MHz. The picture elements shown at A and B
therefore have a length of 1/6 μsec each and a character thus has a
width of 1 μsec.
When the rate of the reference clock pulses
increases, the rate of the display clock pulses also increases and the
character width decreases. Without changing the character width the
above-described character generator can also be used without any
essential changes if the rate of the reference clock pulses is an
integral multiple of 6 MHz. In that case the desired display clock
pulses can e derived from the reference clock pulses by means of a
divider circuit with an integral dividing number. However, there is a
complication if f 0 is not a rational multiple of 6 MHz, for example, if f 0
=13.5 MHz and each character nevertheless must have a width of
substantially 1 μsec. Two generator circuits and a plurality of
converter circuits suitable for use in the character generator shown in
FIG. 3 and withstanding the above-mentioned complication will be
described hereinafter.
FIG. 4 shows an embodiment of the
generator circuit 944 and the converter circuit 942. The reference clock
pulses TR are assumed to occur at a rate of 13.5 MHz. To derive the
desired display clock pulses from these reference clock pulses, the
generator circuit 944 comprises a modulo-N-counter circuit 9441 which
receives the 13.5 MHz reference clock pulses TR indicated at A in FIG.
5. The quantity N is chosen to be such that N clock pulse periods of
the reference clock pulses substantially correspond to the desired
character width of, for example, 1 μsec. This is the case for N=14,
which yields a character width of 1.04 μsec.
An encoding
network 9442 comprising two output lines 9443 and 9444 is connected to
this modulo-N-counter circuit 9441. This encoding network
9442 each time supplies a display clock pulse in response to the
first, the third, the sixth, the eighth, the eleventh and the
thirteenth reference clock pulse in a group of fourteen reference
clock pulses. More particularly the display clock pulse, which is
obtained each time in response to the first reference clock pulse of a
group, is applied to the output line 9443, whilst the other display
clock pulses are applied to the output line 9444. Thus, the pulse
series shown at B and C in FIG. 5 occur at these output lines 9443 and
9444, respectively.
The converter circuit 942 is constituted
by a shift register circuit 9420 comprising six shift register
elements each being suitable for storing a character picture element
code CH(.) which is supplied by the memory medium 941 (see FIG. 3).
This shift register circuit 9420 has a load pulse input 9421 and a
shift pulse input 9422. The load pulse input 9421 is connected to the
output line 9443 of the encoding network 9442 and thus receives the
display clock pulses indicated at B in FIG. 5. The shift pulse input
9422 is connected to the output line 9444 of the encoding network 9442
and thus receives the display clock pulses indicated at C in FIG. 5.
This converter circuit operates as follows. Whenever a display
clock pulse occurs at the load pulse input 9421, the six character
picture element codes CH(.) are loaded into the shift register circuit
9420. The first character picture element code CH(1) thereby becomes
immediately available at the output. The contents of the shift
register elements are shifted one position in the direction of the output by each display clock pulse at the shift pulse input 9422.
Since
the display clock pulses occur at mutually unequal distances, the
time interval during which a character picture element code is
available at the output of the shift register circuit is longer for
the one character picture element code than for the other. This is
shown in the time diagrams D of FIG. 5. More particularly the diagrams
show for each character picture element code CH(.) during which
reference clock pulse periods the code is available at the output of
the shift register circuit. The result is that the picture elements
from which the character is built up upon display also have unequal
lengths as is indicated at D and E in FIG. 2.
The same
character display is obtained by implementing the converter circuit
942 and the generator circuit 944 in the way shown in FIG. 6. The
generator circuit 944 again comprises the modulo-N-counter circuit
9441 with N=14 which receives the 13.5 MHz reference clock pulses TR
shown at A in FIG. 7. An encoding network 9445 is also connected to
this counter circuit, which network now comprises six output lines
9446(.). This encoding network 9445 again supplies a display clock
pulse in response to the first, the third, the sixth, the eighth, the
eleventh and the thirteenth reference clock pulse of a group of
fourteen reference clock pulses, which display clock pulses are
applied to the respective output lines 9446(1), . . . , 9446(6). Thus,
the pulse series indicated at B, C, D, E, F and G in FIG. 7 occur at
these outputs.
The converter circuit 942 has six latches
9423(.) each adapted to store a character picture element code CH(.).
The outputs of these latches are connected to inputs of respective AND
gate circuits 9424(.). Their outputs are connected to inputs of an OR
gate circuit 9425. The AND gate circuit is 9424(.) are controlled by
the control signals S(1) to S(6), respectively, which are derived by
means of a pulse widening circuit 9426 from the display clock pulses
occurring at the output lines 9446(.) of the encoding network 9445 and
which are also shown in FIG. 7. Such a control signal S(i) determines
how long the character picture element code CH(i) is presented to the
output of the OR gate circuit 9425 and hence determines the length of
the different picture elements of the character on the display
screen.
As is shown in FIG. 6, the pulse widening circuit 9426
may be constituted by a plurality of JK flip-flops 9426(.) which are
connected to the output lines of the encoding network 944, in the
manner shown in the Figure. It is to be noted that the function of the
pulse widening circuit 9426 may also be included in the encoding
network 9445. In that case this function may be realized in a different
manner.
In the above-described embodiments of the converter
circuit 942 and the generator circuit 944 the character generator
supplies exactly contiguous picture elements on the display screen.
This means that the one picture elements begins immediately after the
previous picture element has ended. The result is that round and
diagonal shapes become vague. It is therefore common practice to
realize a rounding for such shapes. This rounding can be realized with
the converter circuit shown in FIGS. 4 and 6
by ensuring that two consecutive picture elements partly overlap each
other. This is realized in the converter circuit shown in FIG. 4 by
means of a rounding circuit 9427 which receives the character picture
element codes occurring at the output of the shift register circuit
9420. This rounding circuit 9427 comprises an OR gate 9427(1) and a D
flip-flop 9427(2). The T input of this flip-flop receives the clock
pulses shown at E in FIG. 5, which pulses are derived from the
reference clock pulses TR by means of a delay circuit 9427(3). This
circuit has a delay time t 0 for which a value in the time
diagram indicated at E in FIG. 5 is chosen which corresponds to half a
clock pulse period of the reference cock pulses. The character
picture element codes supplied by the shift register circuit 9420 are
now applied directly and via the D flip-flop 9427(2) to the OR gate
which thereby supplies the six character picture element codes CH(.)
in the time intervals as indicated at F in FIG. 5. The result of this
measure for the display of the character with the letter A is shown at
F in FIG. 2.
The same rounding effect can be realized by means of the converter circuit shown in FIG. 6, namely by providing it with a rounding circuit as well. This is shown in FIG. 8. In this FIG. 8 the elements corresponding to those in FIG. 6 have
the same reference numerals. The converter circuit 942 shown in FIG. 8
differs from the circuit shown in FIG. 6 in that the said rounding
circuit denoted by the reference numeral 9428 is incorporated between
the pulse widening circuit 9426 and the AND gate circuits 9424(.). More
particularly this rounding circuit is a pluriform version of the
rounding circuit 9427 shown in FIG. 4 and is constituted by six D
flip-flops 9428(.) and six OR gates 9429(.). These OR gates receive the
respective control signals S(1) to S(6) directly and via the D
flip-flops. The T inputs of these D flip-flops again receive the version
of the reference clock pulses delayed over half a reference clock
pulse period by means of the delay circuit 94210. This rounding circuit
thus supplies the control signals S'(.) shown in FIG. 7.

An
error correction circuit in a television receiver for receiving, for
example, Teletext information, Viewdata information or information of
comparable systems. The codes representing symbol information received
by the receiver are classified into one out of two or more classes in
dependence on the frequency of their occurrence, this classification
being an indication of the extent to which it is probable that a
received code is correctly received.In
FIG. 1, a picture text television receiver has a receiving section,
audio and video amplifiers 4 and 9 and a picture tube 10, 11. A text
decoder 21 receives symbol information which is stored in a store 25
for display. An error detector circuit 40 including a comparison
circuit 43 and two parity circuits 41 and 42, and checks for parity
between newly received and already stored symbol information. A
reliability circuit 60 is also included.

1. An error
correction circuit for a receiving device for receiving digitally
transmitted symbol information, the transmission of this information
being repeated one or more times, the receiving device having a
decoding circuit for decoding the received information, an information
store coupled to said decoding circuit for storing the information, a
circuit for generating synchronizing signals and a video converter
circuit coupled to said information store and said generating circuit
for converting information and synchronizing signals into a composite
video signal for application to a standard television receiver, a
symbol address in the information store corresponding with a symbol
location on a television picture screen, a symbol location being a
portion of a text line which is displayed with a number of video lines
greater than one, the error correction circuit being coupled to said
decoding circuit and said information store and including means coupled
between said decoding circuit and said information store for checking
newly received symbol information against symbol information stored
in the information store for the corresponding symbol location, a
write-switch having one input coupled to said decoding circuit and an
output coupled to said information store, and a write-setting circuit,
coupled to another input of said write-switch, which determines
whether the newly received information is written or not written into
the information store, said write-setting circit having an input
coupled to said checking means whereby the results of said checking
are a factor in the setting of said write-switch by said write-setting
circuit, characterized in that the error correction circuit further
comprises a classification circuit coupled to the output of said
decoding circuit for classifying a newly received and decoded symbol
in one of at least two classes on the basis of the probability of
occurrence of the newly received symbol, the input of the
classification circuit being coupled to another input of the
write-setting circuit. 2. An
error correction circuit for a receiving device as claimed in claim 1,
characterized in that the write-setting circuit includes a
reliability circuit and the information store comprises an additional
storage element for each symbol address in the information store for
storing a reliability bit associated with that symbol address, inputs
of the reliability circuit being coupled to the classification circuit
and to the information store for accessing the additional storage
elements, for determining, from the additional
storage element corresponding with the symbol address position of
newly received symbol information, a new reliability bit, an output of
the reliability circuit being coupled back to the information store
for writing this new reliability bit into the corresponding additional
storage element when the reliability bit for this symbol address
changes its value. 3. An error
correction circuit for a receiving device as claimed in claim 2,
characterized in that the checking means comprises a comparison circuit
for bit-wise comparing a newly received and decoded symbol with a
symbol read from an address of the information store, this address
corresponding with the symbol location, a comparison output of the
comparison circuit being coupled to a further input of the reliability
circuit. 4. An error correction
circuit for a receiving device as claimed in any one of the preceding
claims, characterized in that the classification circuit comprises a
parity circuit for classifying newly received symbols for respective
particular symbol locations into one of two classes which correspond to
an even and an odd parity respectively, of the newly received
information, and for classifying symbol information already stored in
the corresponding symbol addresses in the information store.
5. An error correction circuit for a
receiving device as claimed in claim 2, characterized in that the
reliability circuit comprises a reliability flipflop and a reliability
read circuit for this flipflop, an output of which also constitutes
the output of the reliability circuit.
6. An error correction circuit for a receiving device as claimed
in claim 1, characterized in that the error correction circuit
comprises a second classification circuit, coupled between said other
classification circuit and said write-setting circuit and having
inputs coupled to said information store, for classifying a symbol
read from the information store.
7. An error correction circuit for a receiving device as claimed in
claim 1 characterized in that the information store comprises, for
each symbol address in the information store, at least one further
storage element for storing the classification associated with the
symbol for that symbol address.

Description:

BACKGROUND OF THE INVENTION
The
invention relates to an error correction circuit of a type suitable
for a receiving device for receiving digitally transmitted symbol
information (picture and/or text), the transmission of this information
being repeated one or more times, the receiving device comprising a
deconding circuit for decoding the received information, an information
store for storing the information, a circuit for generating
synchronizing signals and a video converter circuit for converting
information and synchronizing signals for applying a composite video
signal to a standard television receiver, a symbol address in the
information store corresponding with a symbol location on a television
picture screen, a symbol location being a portion of a text line which
is displayed with a number of videolines greater than one, the error
correction circuit comprising means for checking newly received symbol
information against symbol information stored in the information
store for the corresponding symbol location, together with a
write-switch having a write-setting circuit which determines whether
the newly received information is written or not written into the
information store, the position of the switch being determined on the
basis of the result of said checking.
Error correction
circuits of the above type are used in auxiliary apparatus for the
reception of Teletext transmissions or comparable transmissions, these
auxiliary apparatus being connected to a standard television receiver
either by applying video signals to a so-called video input, or by
applying these video signals, modulated on a carrier, to an aerial
input of the television set. There are already television receivers
with a built-in Teletext receiver already including an error
correction circuit of the above-mentioned type.
The present
Teletext system as it is already used rather widely in the UK, is
based on an 8-bit symbol teletext code having 7 information bits and 1
parity bit; this parity bit is chosen so that each 8-bit symbol in
the code has a so-called "odd" parity, that is to say there is an odd
number of ones in a symbol, and, consequently, also an odd number of
zeros. A display on the television picture screen comprises a "page"
consisting of a number of rows (e.g. 24) of symbols.
Only
symbols with the "odd" parity are stored in the information store.
Each symbol represents either an alpha-numeric or a graphics character
for display on the picture screen, or a control symbol.
If,
in a subsequent transmission cycle for the same symbol location of the
same page, a faulty symbol is detected, then, assuming that only a
single error occurs within a symbol, this faulty symbol will have an
even parity, that is to say a "one" changed into a "zero", or vice
versa, as the result of the error. In this case the information store
is not written into and the old information is retained in the
relevant symbol address.
As the probability is very great that
this old information is correct, the parity check does not only
furnish an error detection, but also an error correction, partly
because of the fact that some knowledge has already been gained from
the previous history. Of course, this does not hold for the first
transmission cycle. Should an "even" parity be found in a 8-bit symbol
in the first transmission cycle, a space ("blank") is generally
recorded in the relevant symbol address and, consequently, displayed
as a space. The easiest way to do this is by filling the entire
information store with space symbols when a new Teletext page is
requested, so that also in the first cycle no information need be
written into the information store on receipt of a symbol having an
"even" parity.
For a poor transmission condition an error
probability of 0.01 is assumed, that is to say one symbol out of a
hundred symbols is received incorrectly. In a complete page having 960
Teletext symbol locations, (i.e. up to 24 rows of up to 40 symbols
per row) the displayed page then shows, after the first cycle, 9 to 10
erroneous spaces on average. In the present system substantially all
these erroneous spaces are likely to have been corrected in the second
cycle.
When the receiving conditions are better, this
situation is already correspondingly more favourable in the first
cycle. Even in the poorest receiving conditions, it appears that the
number of double errors is so small that they may be neglected. Double
errors therefore are hardly ever taken into consideration hereafter.
It will be apparent that in this system each symbol has a certain
degree of redundancy in the form of the parity bit, but this is
off-set by the drawback that the 8-bit code, which has 256 (=2 8 ) combinations, is utilized for only 50% of this capacity, i.e. only for the 128 symbols having "odd" parity.
Although,
for the U.K. itself, such a code has a sufficient capacity to contain
all desired symbols for control, graphics elements, letters, figures,
punctuation marks, etc. as required for Teletext and also, for
example, for Viewdata, it is not possible to allot a specific symbol
to all of the special characters occurring in various other languages.
Several European languages,
in so far they are written in latin characters, have all sorts of
"extra" characters, for example Umlaut letters, accent letters, etc.
When all these extra characters are totalled, including Icelandic,
Maltese and Turkish, then it appears that a total of approximately 220
symbols is required, namely the 128 known symbols plus further
symbols for these "extra" characters.
Several solutions have
been proposed to solve this, but so far none of these have been
satisfactory as they are either very cumbersome or allow only one
language within one page, so that it is impossible or very difficult
e.g. to quote foreign names in a page of text.
Alternatively
it has been proposed--and this is of course very obvious--to use the
entire 8-bit code for symbols. As the redundancy in the code has now
been reduced to zero, no correction can be effected in the second cycle.
If two codes for one symbol location differ from one another in
different transmission cycles, it is theoretically impossible to decide
with certainty which one of the two codes is correct. An additional
information store is required to enable a comparison between a newly
received symbol in the third cycle and a symbol from the second and the
first cycles, and to take the frequently used majority decision
thereafter. This is possible, but three reading cycles are necessary
before the number of errors is reduced to an acceptable level. As each
transmission cycle of a completely full magazine (i.e. a plurality of
pages) takes approximately 25 seconds, the correct text is not known
until after approximately 75 seconds.
As the present system
displays the text correctly after approximately 50 seconds already, such
a solution would mean an increase in the so-called access time.
If
a new parity bit were added to the 8-bit code, each symbol would
require 8+1=9 bits so that it is no longer possible, as is done in the
present system, to accommodate the symbols for one text line of 40
characters in one video line, whereas on the other hand the average
transmission rate decreases if more video lines are needed for the
information transmission. This solution is generally considered to be
unacceptable, also because the compatibility with existing receivers
would be fully lost.
Although any language to be displayed can
be considered to contain redundancy both as regards text and graphics,
so that a viewer may "overlook" many errors, in the sense that there
is still an intelligible display, this does not offer a satisfactory
solution.
SUMMARY OF THE INVENTION
It is the object
of the invention to provide an error correction circuit of the type
referred to for a receiving device for Teletext and comparable systems,
which offers such a solution for the problem outlined above that also
for an 8-bit code without a parity bit substantially all errors, if
any, can be corrected in the second transmission cycle which is
received.
According to the invention an error correction
circuit of the type referred to is characterized in that it comprises at
least one classification circuit for classifying a newly received and
decoded symbol in one of at least two classes on the basis of the
probability of occurrence of the newly received symbol, an output of the
classification circuit being coupled to an input of the write-setting
circuit.
The classification circuit utilizes the hitherto
unrecognized fact that the "language" used for the Teletext system and
for associated systems comprises a third form of redundancy, namely the
frequency with which the different symbols occur in any random text.
From counts performed on longer texts in several languages,
including texts that quote words or names from other languages, it is
found that, on average, these texts did not contain more than
approximately 5% "extra" symbols, in spite of the fact that the extra
symbols constitute approximately 50% of the different code
combinations. The remaining 95% are symbols from the original 50% of
the different code combinations, that is to say control, graphics and
text symbols which were already used in the existing system. For
simplicity, these latter symbols are hereinafter denoted A-symbols,
and the "extra" symbols are denoted B-symbols.
If now an
A-symbol is received in the first cycle and a B-symbol in the second
cycle, or vice versa, it is already possible to decide with a high
degree of certainty which of the two is correct.
Let us assume
that an identified A-symbol is transmitted from the transmitter end
for the same symbol location in those first and second cycles, whereas
the receiver receives an A-symbol in the first cycle and a B-symbol
in the second cycle.
It can be seen that some form of A-symbol
is obtained in the receiver when either a real A-symbol is properly
received or a real B-symbol is erroneously received. Assuming there is
an error probability of 0.01, the probability that the
first-mentioned situation occurs is 0.95×0.99=0.9405 and the
probability that the second situation occurs is 0.05×0.01=0.0005 so
that the probability that an A-symbol is received totals 0.941. A
B-symbol results from a real B-symbol (0.05×0.99=0.0495) or a faulty
A-symbol (0.95×0.01=0.0095), adding up to a total probability of
0.059. Of course 0.941+0.059=1.000, based on the assumption that
double errors do not occur, so that any A-symbol A x will never be received as another A-symbol A y
from the same class. The probability that a received A-symbol is
correct is 0.9405/0.941=0.9995. The probability that a received B-symbol
is correct is 0.0495/0.059=0.839.
For the above mentioned
case, it is correctly assumed that the A-symbol in the first cycle is
correct, and that the B-symbol in the second cycle is incorrect.
Consequently,
there is an A-symbol in the information store in both cycles. In the
second cycle the B-symbol must not be stored, and the A-symbol
obtained from the first cycle must be retained.
Should a
B-symbol be received first, then a B-symbol is written into the
information store, (the probability that this B-symbol is correct is
still 84%) but it is not retained in the second cycle, and the
A-symbol received in the second cycle must now be recorded in the
information store.
At the end of the second cycle it is seen
that in this manner the then remaining error is less than one in
approximately 5 full pages, as applied to the Teletext system. Such a
number of errors is so small that apparently they are not noticed by a
viewer.
When an A-symbol is received in the first cycle and
in the second cycle or a B-symbol is received in both cycles then
there is no doubt, after symbol sequences A, B or B, A there is little
doubt, but the symbol stored in the information store must be
considered to be somewhat suspect. This also applies to each B-symbol
recorded in the first cycle, which may lead to a further improvement
when a decision is taken.
Another advantageous embodiment of
an error correction circuit according to the invention is
characterized in that the error correction circuit comprises a
reliability circuit and the information store comprises an additional
storage element for each symbol address in the information store for
storing a reliability bit associated with that symbol address, inputs
of the reliability circuit being coupled to the classification circuit
and to a read circuit for the additional storage elements, for
determining from the additional storage element corresponding with the
symbol address of newly received symbol information a new reliability
bit, this new reliability bit being written at least into the
corresponding additional storage element when the reliability bit for
this symbol address changes its value.
When the transmitter
successively transmits an A-symbol for a certain symbol and location and
symbols ABA are successively received, then the A-symbol may be
recorded as being "non-suspect" after the first cycle, indicated by an R
(reliable) hereinafter. An R' after the second (A), the brackets
indicating that the information is retained (not written into the
information store) indicates the assumed non-reliability of this
retained (A)-symbol, and an A and an R in the third cycle indicates the
reliability of the correctly received A-symbol. The A-symbol in the
information store is now again assumed to be reliable for this symbol
sequence.
In like manner, when the transmitter transmits a B
for a certain symbol location, and the symbols B, A, B, B are
successively received, symbols and reliability states B. R', A.R', B. R'
and B.R are recorded.
All this depends on the decision logic opted for.
It
is assumed here that the possibility of an error for the same symbol
location in two consecutive cycles is also extremely small; when the
transmitter transmits symbols A, A, A, A in successive cycles, the
probability that the receiver would receive, for example, symbols A, B,
B, A is assumed to be zero. From practical experiments it was seen
that this form of a double error can be fully neglected.
This
improvement makes it of course necessary for reliability state R or R'
to be retained together with the related symbol in the information
store and that it must be revised every cycle, if necessary. Each
symbol address now has 9 bits instead of 8 in the Teletext receiver
memory. This has hardly any consequences for the price as a standard
RAM having a capacity of 1kx9 can be used.
As is apparent from
the foregoing examples, it can be advantageous to make different
decisions in the case a symbol sequence B-A is formed after the first
cycle or after a further cycle.
A further advantageous
embodiment of an error correction circuit is characterized in that the
error correction circuit comprises a counting circuit for counting
information transmission cycles following a new request for (always) a
full picture of the requested symbol information, a counting output
of this counting circuit being coupled at least to another input of
the reliability circuit, this counting output being, for example, also
coupled to a further input of the write-setting circuit.
As
seen earlier in the history of data transmission and information
processing equipment, the need was felt also for Teletext and
comparable systems, to realise the extension with new symbols by
doubling the number of symbols identified by an n-bit code, in such a
way that the original symbols retain as far as possible their existing
bit combustion.
This results inter alia in that transmission
in a new, extended, code are also displayed reasonably well by
existing receivers. A receiver for the original symbols only allots
the correct symbol to approximately 95% or more of the symbol
locations in the display. A limited compatability is therefore still
possible, and even a full compatibility if a normal "English" text is
transmitted.
In the example considered herein all the original symbols remain the same, and all the "extra" symbols have even parity.
This symbol set is now under discussion as an international standardization proposal.
It
will be apparent that in the last-mentioned case no intricate
classification circuit is required to decide for each symbol whether
this symbol must be allocated to the A or to the B group.
A
further advantageous embodiment of an error correction circuit according
to the invention is therefore characterized in that the
classification circuit comprises a parity circuit for classifying
newly received symbols for respective particular symbol locations into
one of two classes which correspond to an even and an odd parity,
respectively, of the newly received information, and for classifying
symbol information already stored in the corresponding symbol
addresses in the information store.
This results, at first
sight, in very strange circuit, as now a parity check is performed on a
code which contains no parity bit at all.
It is, of course,
alternatively possible to record the relevant classification of a
symbol in the information store, but this requires at least a tenth
bit for each symbol address and, for a classification in more than two
groups, it requires even more. It is, however, more advantageous,
when a newly received symbol for a particular symbol location is
compared with the symbol already stored in the corresponding symbol
address of the information store, to determine the classification of
the symbol again when it is read from the address, as this requires
less material and the advantage that a standard 1 Kx9 RAM can be used
is retained.
A further advantageous embodiment is
characterized in that the error correction circuit comprises a second
classification circuit for classifying a symbol read from the
information store.
In the most advantageous case, wherein all extra symbols are even parity codes, this means a second parity check circuit.
In
the case that classification in two classes coincides with an even
and an odd parity, respectively, of the symbols, it furthermore
appears to be possible to enter the classification in the information
store in such a way that the notation of the classification does not
require an additional storage bit.
An embodiment of an error
correction circuit according to the invention, which is advantageous
for this case, is characterized in that the error correction circuit
comprises a modification circuit which after having determined the "0"
or "1" parity value of a newly received symbol means of the parity
circuit replaces the content of a fixed bit position of the newly
received symbol by this parity value.
Any random bit can be
selected as the fixed bit position in the symbol, for example, the
eight bit in the case of an 8-bit symbol, whereas a ninth bit is used
as, for example, the reliability bit.
There are four distruct possibilities:

TABLE I

______________________________________

Modified Class Symbol (n+1) Parity symbol (n+1) Parity

______________________________________

A xxxxxxx 1 1 xxxxxxx 1 1

A xxxxxxx 0 1 xxxxxxx 1 0

B xxxxxxx 1 0 xxxxxxx 0 1

B xxxxxxx 0 0 xxxxxxx 0 0

______________________________________

In this case only one 8-bit parity circuit is needed.
It
is of course alternatively possible to realize the second
classification circuit virtually by using the first classification
circuit twice on a time-sharing basis, first as the first and then as
the second classification circuit. This requires some additional control
logic and some additional time, so that the provision of a second
classification circuit will be preferred, especially in the case where a
simple parity check is performed.
The above-mentioned
solution with its possible extensions will furnish the best result if
all these extensions are provided. This is at the same time the most
expensive solution. Error correction circuits which do not have all the
above-described extensions are cheaper and hardly less good.
DESCRIPTION OF THE DRAWINGS
One
specific combination will now be discussed in greater detail by way
of example with reference to the drawings. On the basis thereof, any
other combination can be easily implemented by one skilled in the art.
In the drawings:
FIG. 1 shows a simplified block
diagram of a television receiver comprising a Teletext receiving
section including an error correction circuit according to the
invention.
FIG. 2 shows a simplified time diagram in which a
number of different error combinations is shown in an exaggerated burst
of errors.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The
embodiment chosen for FIG. 1 is suitable for reception in accordance
with the proposed new code and comprises two clasification circuits
consisting of two parity circuits, a comparison circuit for the bit-wise
comparison of two symbols, a reliability circuit comprising a
reliability flipflop and, in addition, the elements already known for a
television plus Teletext receiver.
FIG. 1 shows a television receiver by means of a simplified block diagram. A
receiving section 1 having an aerial input 2 comprises the
high-frequency receiving section, the intermediate-frequency amplifier
section, the detection and the synchronizing circuits of the receiver.
An audio output 3 is coupled to one or more loudspeakers 5 via an
audio amplifier 4. Via control switches 7 and 8 a video output 6 is
coupled for normal television reception to a video amplifier 9 for a
picture tube 10 comprising the picture screen 11. Via a control switch
13 a synchronizing output 12 is coupled during normal television
reception to a time-base circuit 14 which supplies the deflection
voltages for the picture tube 10 via an output 15.
However, the control switches 7, 8 and 13 are shown in the position for Teletext reception and display.
Via
the switch 7 the video signal is applied to an input 20 of a Teletext
decoder 21, a synchronizing input 22 of which is coupled to the
synchronizing output 12 of the receiving section 1.
In the
Teletext decoder 21, serially received Teletext symbols are successively
entered in parallel into a buffer register 23 thereof. Depending on
the action decided upon, the contents of the buffer register 23 can be
transferred to a storage register 24 of an information store 25, and
from the storage register 24, the consecutive symbol addresses each
corresponding to a symbol location on the picture screen 11 are filled,
until the entire information store 25 is filled with the symbol
information which corresponds to the desired Teletext page.
This
and also the further processing operations are fully in agreement
with the existing Teletext system. Addressing, reading of the
information store, etc. are therefore not further described.
An
output 26 of the information store 25 is coupled to a video
(Teletext) generator 27, an output 28 of which is connected to the
video amplifier 9 via the switch 8. In addition, there is provided in
known manner a signal generator 29 and a generator 30 for generating
several timing signals required in the receiver, which are applied to
several other elements via outputs 31 to 35, inclusive. Synchronizing
signals which can be applied to the time-base circuit 14 via the
switch 13 are produced at the output 32.
The decision whether
the content of the buffer register 23 must be transferred or not
transferred to the storage register 24 is taken by an error correction
circuit, which would, in the known Teletext system, consist of a
parity check circuit.
The error correction circuit according
to the invention consists of an error detection circuit 40 and, in the
specific embodiment being described, a reliability circuit 60. The
error detection circuit 40 comprises a parity circuit 41 for the
buffer register 23, a parity circuit 42 for the storage register 24, a
comparison circuit 43 for comparing the contents of buffer and
storage registers 23, 24 with one another, and a number of write
switches 44-0 to 44-7 inclusive. In this example these write switches
are represented as respective AND-gates each having two
inputs and an output. An input 45-i of each of the write switches is
always connected to a corresponding output 46-i of the buffer register
23, these outputs also being connected respectively to inputs 47-1 to
47-8 inclusive, of the parity circuit 41 and to inputs 48-0 to 48-7
inclusive, of the comparison circuit 43.
The other input 49-i
of each of the write switches is connected to a common write command
input 50 of the error detection circuit 40.
In addition, output
51-i of the storage register 24 are connected to respective inputs
52-1 to 52-8 inclusive, of the parity circuit 42 and to corresponding
further inputs 53-i of the comparison circuit 43 and to outputs 54-i
of the write switches 44-0 to 44-7.
An odd parity-output 55
("1" for odd-parity) of the parity circuit 41, is connected to an
input 52-9 of the additional parity circuit 42, which has an output 56
for even or odd parity at the inputs 52-1 to 52-9, inclusive.
A
Signetics IC No. 54180 or No. 8262 may, for example, be used for the
parity circuit 41. If the parity of the symbol in the buffer register
23 is odd or even, a "1" and "0", respectively, appears at the output
55.
A Signetics IC No. 8262 may also be used for the parity
circuit 42. If the parity of the symbol in the storage register 24 is
odd and a "1" has appeared at the output 55, then a "1" appears at the
output 56 for the even parity of the parity circuit 42, that is to
say both symbols had an odd parity. If both symbols have an even
parity the input 52-9 receives a zero, so that the total number of
ones is even again and the output 56 shows an "1" again. Should the
parities of the buffer register 23 and the storge register 24 be
unequal, then the output 56 shows "0".
Thus the output 56
(Even Parity) may be considered to be an output which indicates by
means of the "1", that the investigated symbols have an equal parity
(Equal Parity, EP).
The comparison circuit 43 has an output 57
which becomes a "1" as soon as all the bits of the compared symbols
are mutually equal. The signal thus obtained will be denoted EB (Equal
Bytes).
The reliability circuit 60 comprises a flipflop 61
having number of writing gates 62. A JK flipflop is chosen for the
described example but this is not essential to the inventive idea. One
half of a Signetics 54112 may, for example, be used as a JK flipflop.
Descriptions, truth tables and time diagrams of the above-mentioned
Signetics circuits are known from the Philips Signetics Data Handbook.
The reliability circit 60 satisfies the following equations:
CK R =CLK, obtained from the clock signal generator 29. J R =R/WR G +(R/W)'EP (I) K R =R/WR G +(R/W)'EB (II)
in which R G is the reliability status as stored in the memory 25, The operation of the JK-flipflop can be explained as follows, reference also being made to the time diagram of FIG. 2. Within
successive periods of approximately 25 seconds the symbols for 960
symbol locations (i.e. a page of text) are repeatedly received. The
solid line sections 100 represent the symbol processing of the symbol S x in consecutive cycles 0 to 7, inclusive, indicated as S x ,0 to S x ,7 inclusive. The broken line sections represent in a very concise manner the processing of S 0 to S x -1, inclusive, and S x +1 to S 959 ,
inclusive, one processing period comprising, for example, two cycles
of the clock signal 101 of the clock signal generator 29 and one
read/write cycle consisting of the portions R/W and (R/W)', read and
write respectively, controlled by the signal 102, obtained from the
output 31 of time signal generator 30. During the read portion 103 of
cycle 102 the contents of a symbol address which correspond with the
signal combination entered in the buffer register 23 for a given symbol
location, is entered into the storage register 24. As each symbol
address has a ninth bit for a reliability bit, a status value R G
appears simultaneously at an output 63 of the information store 25.
On the first rising clock edge 104 only the first terms of the
equations I and II are operative, as R/W="1" and consequently
(R/W)'="0". This means that at the instant 104 the flipflop 61, R
assumes the value "1" when R G ="1" and the value "0" when R G
="0", as shown in the line sections 105. At the next clock edge 106
only the second terms are operative, and the flipflop 61 can now
retain the previously adjusted value or assume the other value. This
final value at the output 64 of the flipflop 61 is applied to an input
65 of the information store for writing a next R G in the ninth bit of the corresponding storage address.
The
output 66 (R') of the flipflop 61, which is connected to thewrite
command signal input 50 of the error detection circuit 50, further
determines whether the contents of the buffer register 23 can be
transferred to the storage register 24 during the write cycle 107 (see
FIG. 2).
Finally, the lines 108, 109 of FIG. 2 represent two
bit contents of the storage register and 110, 111 represent two bit
contents of the buffer register. For clarity's sake the remaining bits
have been omitted.
The signal EP is denoted by 112, and the signal EB by 113.
In this example the following set of decision rules has been realised in the circuit.

TABLE II

______________________________________

Decision Read Write SR EP EB R G 23➝24 Written S R K R

______________________________________

1 0 0 0 1 0 0 x

2 1 0 0 1 1 1 x

3 1 1 0 1 1 1 x

5 1 1 1 0 1 x 1

6 1 0 1 0 0 x 0

7 0 0 1 0 0 x 0

(4) 1 0 0 1 0 0 x

______________________________________

The states, indicated by an x, of J R and K R
are irrelevant for the position of the flipflop. The equations I and
II have been chosen thus that the required values "0" and "1" for J R and K R are produced. FIG.
2 shows the states and EP, EB and R in the line sections 112, 113 and
105, respectively, by means of an example which shows an unprobable
burst of received errors, such that each one of the decisions occurs at
least once.
When the first cycle starts, the entire
information store 25 is filled with space symbols. The space symbol is
an A-symbol, denoted in FIG. 2 by A. It is assumed that the
transmitter transmits a B-symbol and continues to do so. A faulty
B-symbol has the same parity as A and is denoted by B'. On the basis
of decision 1, EP=0, EB=0 and R G ="0" in the second half
of the cycle a B' (erroneously received B with an even number of
errors) is written into the storage register 24. The new R G remains "0" because J R =0, K R =x.
In
the next cycle the buffer register 23 contains a correctly received
B, which is transferred to the storage register 24 in accordance with
decision 2.
The further cycles need no explanation. (B)
indicates when there is no transfer to the store. The B already present
in the relevant symbol address is not changed.
Throughout the example of the transmitter
transmitted: B B B B B B B B
received: B' B B' B B A B B
dislayed: B' B (B) B B (B) B B
The displayed error B' in the first cycle can of course not be avoided in this example, all following results are correct.
Any other possible received sequence can be followed in a similar manner.
Two of the decisions need some further explanation.
Decision
2 with EP="1" and EB="0", seems to indicate a multiple and,
consequently, very rare error. As the information store 25 is initially
filled with A's and the probability that an A will be received is
high, this "error" will occur very frequently, especially in the first
cycle.
Any double error occurring at a later instant will be treated likewise, in that very rare event.
Decision 6 deals with an equally rare event, but with R G
="1". It shortens the elimination of a multiple error, but will be
rarely necessary. However, this decision 6 can be combined cheaply with
decision 7.
In the embodiment explained on the basis of Table I the processing of EP in particular is simplified.
The following simple process can now, for example, be applied.
A newly received symbol is applied to the input of the parity circuit 41.
If
the newly received symbol (n+1) is a symbol from the A group, then
the parity circuit 41 indicates an odd parity that is to say a "1" at the output "odd parity".
This "1" is transferred to the eight bit of the buffer register 23.
By
comparing a corresponding symbol (n) from the information store 25
with a modified symbol (n+1), EP can now be found by comparing the two
eights bits of the buffer register 23 and the storage register 24. EB
can be determined as previously to detect whether there is or there is
not a difference between the two (modified) symbols.
In
dependence on EP, EB and R, it is decided in a conventional manner
whether the modified symbol will be written or not written into the
information store 25. Thus the information store 25 comprises modified
symbols only, so that in checking with the comparator 43, this check
must be made against the also modified, newly received symbol.
During
the display of the page, the parity circuit 41 is available for
remodification, it only being necessary to invert the eighth bit if the
eighth bit of the symbol to be displayed differs from the parity of
this symbol, that is to say it is sufficient to replace the eighth bit
of the storge register 24 by the parity now found..
A slight
improvement can still be obtained by means of the additional decision
(see at the bottom of the Table II). However, to enable the use of this
additional decision, instead of decision 2 which can then only hold
for the first cycle, a cycle counter must now be incorporated which
forms with New Request="1" an additional condition for decision 2 and
which, in all subsequent cycles with NR="0" results in decision 4 when
EP=1, EB=0 and R G =0.
In view of what was
described herefore such an extension can be easily realized by one
normally skilled in the art of logic design.
In extremely rare cases this embodiment results in a further small improvement.
A
simplified embodiment produces for all normal single errors an
equally satisfactory result but it deals with the multiple errors in a
less satisfactory way. However, the total result remains very
satisfactory for the user.
The entire comparison circuit is omitted from this simplified embodiment. The decision table is now reduced to:

TABLE III

______________________________________

Read Write Written Decision EP R G 23-24 R G

______________________________________

1A 1 0 1 1

2A 1 1 1 1

3A 0 0 1 0

4A 0 1 0 0

______________________________________

Again this embodiment can be easily realized by one normally skilled in the art, using what has been described herein.
The
same applies if smll changes are desired in the decisions, and also
when, for example, the circuit must be implemented in the form of one
or more Large Scale Integrated circuits (LSI), or when it is realized
wholly or partly by means of a micro-processor.

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Resisting the tide of post-modernity may be difficult, but I will attempt it anyway.

Your choice.........Live or DIE.That indeed is where your liberty lies.

IMPORTANT NOTE: - FRANK SHARP obsoletetellyemuseum.blogspot.comwas founded as a public free WEB Museum to all kind of people and amateur and professional CRT TELEVISION Lovers who enjoy using and/or preserving - restoring vintage CRT Televisions sets, or only curious public who was unaware of that kind of technolgy of the past. The purpose is to provide information about vintage Television Receivers Publicy on the WEB that is generally difficult to locate; all this as a important milestone general worldwide reference for the future, globally in the public interest.obsoletetellyemuseum.blogspot.com does not provide support or parts for any apparatus on this site nor do we represent any manufacturer listed on this site in any way. Catalogs, manuals and any other literature that is available on this site is made available for a historical record only. Please remember that safety standards have changed over the years and information in old manuals as well as the old Television receivers themselves may not meet modern standards. It is up to the individual user to use good judgment and to safely operate old machinery. The obsoletetellyemuseum.blogspot.com web site will assume NO responsibilities for damages or injuries resulting from information obtained from this site. No offer to sell or license — Nothing in this site/Blog may be interpreted or construed as an offer to sell products that is open for acceptance or the grant, conveyance or implication of any license under any copyrights, patents or other industrial or intellectual property rights.

Many topics are permanent, so may be updated to any material, for add or correct info.

Sure Fun Times, A working TV Discovered with a CRT Oscilloscope !

Safety Hazards:

------------------------------------------------------Safety Hazards in Radio and TV Repair,------------------------------------------------------

People who believe they can conquer nature are clueless that the laws of nature are a precondition of their existence. Their weapon is a miserable idea.When man attempts to rebel against the iron logic of Nature, he comes into struggle with the principles to which he himself owes his existence as a man. And this attack must lead to his own doom.

Anyone attempting to repair any electronic equipment who does not fully understand the shock hazards, as well as the fire hazards associated with working with electronic equipment, should not attempt such procedures! Improperly attempted repair can kill you and burn down your house.Devices that plug into the wall can produce a very lethal electric shock as well cause a fire from incorrect or careless repairs both during servicing or later on.Improper repair of battery operated devices can also result in bad consequences for you, the device, and any equipment attached to it.

Why some people do repairs themselved then? If you can do the repairs yourself, the equation changes dramatically asyour parts costs will be 1/2 to 1/4 of what a professional will chargeand of course your time is free. The educational aspects may also beappealing. You also will learn a lot in the process.

Consumer electronic equipment like TVs, computer monitors, microwave ovens, and electronic flash units, use voltages at power levels that are potentially lethal. Even more so for industrial equipment like lasers and anything else that is either connected to the power line, or uses or generates high voltage.

Normally, these devices are safely enclosed to prevent accidental contact. However, when troubleshooting, testing, making adjustments, and during repair procedures, the cabinet will likely be open and/or safety interlocks may be defeated. Home-built or modified equipment, despite all warnings and recommendations to the contrary - could exist in this state for extended periods of time - or indefinitely.

Depending on overall conditions and your general state of health, there is a wide variation of voltage, current, and total energy levels that can kill.

Microwave ovens in particular are probably THE most dangerous household appliance to service. There is high voltage - up to 5,000 V or more - at high current - more than an amp may be available momentarily. This is an instantly lethal combination.

TVs and monitors may have up to 35 kV on the CRTbut the current isn't low - like a wrong legend saying a "couple of milliamps" but relatively high because of the boost circuit technology and transformer design. However, the CRT capacitance can hold a painful charge for a long time. In addition, portions of the circuitry of TVs and monitors as well as all other devices that plug into the wall socket are line connected.This is actually even more dangerous than the high voltage due to the greater current available - and a few hundred volts can make you just as dead as 35 kV!

Electronic flash units and strobe lights, and pulsed lasers have large energy storage capacitors which alone can deliver a lethal charge - long after the power has been removed. This applies to some extent even to those little disposable pocket cameras with flash which look so innocent being powered from a single 1.5 V AA battery. Don't be fooled - they are designed without any bleeder so the flash can be ready for use without draining the battery!

Even some portions of apparently harmless devices like VCRs and CD players - or vacuum cleaners and toasters - can be hazardous (though the live parts may be insulated or protected - but don't count on it!

This information also applies when working on other high voltage or line connected devices like Tesla Coils, Jacobs Ladders, plasma spheres, gigawatt lasers, hot and cold fusion generators, cyclotrons and other particle accelerators, as well as other popular hobby type projects. :-)

In addition, read the relevant sections of the document for your particular equipment for additional electrical safety considerations as well as non-electrical hazards like microwave radiation or laser light. Only the most common types of equipment are discussed in the safety guidelines, below.

SAFETY guidelines:

These guidelines are to protect you from potentially deadly electrical shock hazards as well as the equipment from accidental damage.

Note that the danger to you is not only in your body providing a conducting path, particularly through your heart. Any involuntary muscle contractions caused by a shock, while perhaps harmless in themselves, may cause collateral damage. There are likely to be many sharp edges and points inside from various things like stamped sheet metal shields and and the cut ends of component leads on the solder side of printed wiring boards in this type of equipment. In addition, the reflex may result in contact with other electrically live parts and further unfortunate consequences.

The purpose of this set of guidelines is not to frighten you but rather to make you aware of the appropriate precautions. Repair of TVs, monitors, microwave ovens, and other consumer and industrial equipment can be both rewarding and economical. Just be sure that it is also safe!

Don't work alone - in the event of an emergency another person's presence may be essential.

Always keep one hand in your pocket when anywhere around a powered line-connected or high voltage system.

Wear rubber bottom shoes or sneakers. An insulated floor is better than metal or bare concrete but this may be outside of your control. A rubber mat should be an acceptable substitute but a carpet, not matter how thick, may not be a particularly good insulator.

Don't wear any jewelry or other articles that could accidentally contact circuitry and conduct current, or get caught in moving parts.

Set up your work area away from possible grounds that you may accidentally contact.

Have a fire extinguisher rated for electrical fires readily accessible in a location that won't get blocked should something burst into flames.

Use a dust mask when cleaning inside electronic equipment and appliances, particularly TVs, monitors, vacuum cleaners, and other dust collectors.

Know your equipment: TVs and monitors may use parts of the metal chassis as ground return yet the chassis may be electrically live with respect to the earth ground of the AC line. Microwave ovens use the chassis as ground return for the high voltage. In addition, do not assume that the chassis is a suitable ground for your test equipment!

If circuit boards need to be removed from their mountings, put insulating material between the boards and anything they may short to. Hold them in place with string or electrical tape. Prop them up with insulation sticks - plastic or wood.

If you need to probe, solder, or otherwise touch circuits with power off, discharge (across) large power supply filter capacitors with a 2 W or greater resistor of 100 to 500 ohms/V approximate value (e.g., for a 200 V capacitor, use a 20K to 100K ohm resistor). Monitor while discharging and/or verify that there is no residual charge with a suitable voltmeter. In a TV or monitor, if you are removing the high voltage connection to the CRT (to replace the flyback transformer for example) first discharge the CRT contact (under the insulating cup at the end of the fat red wire). Use a 1M to 10M ohm 1W or greater wattage resistor on the end of an insulating stick or the probe of a high voltage meter. Discharge to the metal frame which is connected to the outside of the CRT.

For TVs and monitors in particular, there is the additional danger of CRT implosion - take care not to bang the CRT envelope with your tools. An implosion will scatter shards of glass at high velocity in every direction. There is several tons of force attempting to crush the typical CRT. Always wear eye protection. While the actual chance of a violent implosion is relatively small, why take chances? (However, breaking the relatively fragile neck off the CRT WILL be embarrassing at the very least.)

Connect/disconnect any test leads with the equipment unpowered and unplugged. Use clip leads or solder temporary wires to reach cramped locations or difficult to access locations.

If you must probe live, put electrical tape over all but the last 1/16" of the test probes to avoid the possibility of an accidental short which could cause damage to various components. Clip the reference end of the meter or scope to the appropriate ground return so that you need to only probe with one hand.

Perform as many tests as possible with power off and the equipment unplugged. For example, the semiconductors in the power supply section of a TV or monitor can be tested for short circuits with an ohmmeter.

Provide a reliable means of warning that power is applied and that high voltage filter capacitor(s) still hold a charge during servicing. For example, solder a neon indicator lamp (e.g., an NE2 in series with a 100K ohm resistor) across the line input and a super high brightness LEDs in series with 100K, 1 W resistors across the main filter capacitor(s).

Use an isolation transformer if there is any chance of contacting line connected circuits. A Variac(tm) (variable autotransformer) is not an isolation transformer! However, the combination of a Variac and isolation transformer maintains the safety benefits and is a very versatile device. See the document "Repair Briefs, An Introduction", available at this site, for more details.

The use of a GFCI (Ground Fault Circuit Interrupter) protected outlet is a good idea but may not protect you from shock from many points in a line connected TV or monitor, or the high voltage side of a microwave oven, for example. (Note however, that, a GFCI may nuisance trip at power-on or at other random times due to leakage paths (like your scope probe ground) or the highly capacitive or inductive input characteristics of line powered equipment.) A GFCI is also a relatively complex active device which may not be designed for repeated tripping - you are depending on some action to be taken (and bad things happen if it doesn't!) - unlike the passive nature of an isolation transformer. A fuse or circuit breaker is too slow and insensitive to provide any protection for you or in many cases, your equipment. However, these devices may save your scope probe ground wire should you accidentally connect it to a live chassis.

When handling static sensitive components, an anti-static wrist strap is recommended. However, it should be constructed of high resistance materials with a high resistance path between you and the chassis (greater than 100K ohms). Never use metallic conductors as you would then become an excellent path to ground for line current or risk amputating your hand at the wrist when you accidentally contacted that 1000 A welder supply!

Don't attempt repair work when you are tired. Not only will you be more careless, but your primary diagnostic tool - deductive reasoning - will not be operating at full capacity.

Finally, never assume anything without checking it out for yourself! Don't take shortcuts!

Many people who mistakenly feel that ‘old technology’ is somehow more user-friendly, in some strange way automatically good - merely because it is old. Don’t be fooled! Approach old equipment with an open and alert mind and realise that a hot chassis, or a resistor line cord, or asbestos insulation, or selenium rectifiers require much more thought and consideration for safety.

Live chassis are indiscriminate in whom they kill and even if you are a thoughtful, careful kind of person, that doesn’t mean the last person who handled the set was.

Vintage radio and television receivers use 'live chassis' techniques, in which the chassis is connected directly to one side of the incoming mains supply. This means they can be lethal to carry out repair or servicing work on, unless the appropriate safety measures are in place.

Another thing about live-chassis sets - live spindles. We’ve touched on this already but it’s worth making the point once more. The shafts of switches and potentiometers fixed to the chassis may well be at chassis potential and thus live. The bakelite or wood cabinet is insulated but these shafts are not, and if someone lost the proper grub screw and replaced a knob using a cheesehead screw, the next person to grip that knob may get a dose of 250 volts. Originally these grub screws were sealed and embedded in wax but you cannot rely on subsequent tinkerers having the same high standards.

Even in more orthodox apparatus standards of insulation were not always as high as they are now. Soldered connections to HT and mains wiring should always have rubber or plastic sleeving but in times gone by this was often omitted (or it may since have perished). Beware too of kinked and frayed braiding on cloth-covered mains cords, particularly when the cord has a dropper conductor.

If you are not satisfied that you fully understand the risks involved in this sort of work, do not proceed any further. Instead seek advice and assistance from a competent technician or engineer.

Whenever you acquire a new treasure there's always a terrific temptation to try it out. With mains-driven equipment that means plugging it in and seeing if it works. Well don't, not until you have made some quick checks.

Before contemplating connecting any unknown receiver to the mains supply, spend a little time inspecting it for signs of missing or loose parts, blown fuses, overheating or even fire damage. Use a meter to check obvious points to ensure no short circuit exists (e.g. across the mains input). If you then decide to apply power keep clear but be observant since an elderly electrolytic might explode! This can be avoided if you can apply power gradually through a variac. Auto-transformers are handy for supplying reduced power to sets being repaired but they are not a substitute for a proper isolation transformer!

If you are working with electricity and your work area has a concrete floor, a rubber mat is essential, particularly during damp weather! Where possible try to arrange a neat working area away from water or central heating pipes. For safety try to arrange that this area is separate from the area occupied by your family. This is emphasised because inadvertently rushing to answer a telephone you might just leave a TV chassis connected to a supply and curious little fingers know nothing of the dangers of electricity - or, for that matter - the lethal vacuum encased within every picture tube!

Many younger enthusiasts may not be aware of the dangers of mishandling tubes, in particular the old round types found in early TVs. When handling these tubes eye protection should be worn and tubes must not be left lying around, they must be stored in boxes. The glass is surprising fragile and can implode without any provocation or warning. Bits of glass flying around at high speed can be deadly. The notes following are inspired by Malcolm Burrell again.

Picture tubes are perhaps one of the most hazardous items in any TV receiver. This is because most are of glass construction and contain a very high vacuum. If you measured the total area of glass in any picture tube then estimated the pressure of air upon it at 14.7lb. per square inch, you would discover that the total pressure upon the device could amount to several tons! Fracturing the glass suddenly would result in an extremely rapid implosion such that fragments of glass, metal and toxic chemicals would be scattered over a wide area, probably causing injury to anyone in close proximity. In modern workshops it is now a rule that protective goggles are worn when handling picture tubes.

The weakest point in most picture tubes is where the thin glass neck containing the electron gun is joined to the bowl. It is therefore essential that you refrain from handling the tube by its neck alone. Once a tube is removed from the receiver hold it vertically with the neck uppermost and one hand beneath the screen with the other steadying the device by the neck.With larger devices it is sometimes easier to grip the peripheral of the screen with both hands.

Until the advent of reinforced picture tubes, most were mounted in the cabinet or on the TV chassis by some form of metal band clamped around the face.Never support the weight of the tube by this band since it has been known for the tube to slide out! Some of the larger tubes are extremely heavy. It may, therefore, be easier to enlist assistance.

Before starting to remove a tube, first discharge the final anode connection to the chassis metalwork and preferably connect a shorting lead to this connection whilst you are working. It might be convenient to keep a spare piece of EHT cable with a crocodile clip at one end and a final anode connector at the other.

Exercise care when removing picture tubes from elderly equipment. You may find that the deflection coils have become stuck to the neck. It is extremely dangerous to use a screwdriver prise them away. Gently heating with a hairdryer or soaking in methylated spirit is safer.

Disposal of picture tubes also requires care. Unless rendered safe they should never be placed in dustbins or skips. Many engineers swipe the necks off tubes in cavalier fashion using a broom handle but this is not recommended. A safer method is to make a hole in the side of a stout carton, preferably one designed to hold a picture tube. The tube is placed in the carton and the neck broken using a broom handle. The carton should then be clearly labelled that it contains chemicals and broken glass!

Therefore people who believe they can conquer nature are clueless that the laws of nature are a precondition of their existence. Their weapon is a miserable idea.When man attempts to rebel against the iron logic of Nature, he comes into struggle with the principles to which he himself owes his existence as a man. And this attack must lead to his own doom.

Think for yourself. Otherwise you have to believe what other people tell you.

For most people thinking is a matter of fortune.A society based on individualism is an oxymoron.Freedom is at first the freedom to starve.A wise fool speaks, because he has something to say.A fool speaks, because he has to say something.A wise fool is silent, because there is nothing to say.A fool is silent, because he has nothing to say.

Resist or regretWork for what's good for our people

Help stem the dark tideStand tall or be beat downFight back or die

The man who does not exercise the first law of nature—that of self preservation — is not worthy of living and breathing the breath of life.

We now live in a nation where doctors destroy health, lawyers destroy justice, universities destroy knowledge, governments destroy freedom, the press destroys information, religion destroys morals and our banks destroy the economy.The globalist argument is that if only we erase distinctions, obliterate identities, put everyone on a level playing field, etc.. we can eliminate war and everyone can be so prosperous and efficient, such great cogs in a well-oiled global machine.There will be no more historical grievances because people will no longer even care, they'll have no connection to the past, no foolish pride in past accomplishments of people totally unrelated to them.A globalized culture, no borders, everyone a citizen of the world.Know this: I will never acquiesce to this corrupt, inhuman, Borg-like vision. The dangerous lunatics who push us towards their globalized "utopia" are my enemy. How exactly all this will play out, whether through wars, or whether we can thwart the globalist agenda peacefully (this is my hope of course) I don't know. But I do know that unless people are willing to fight and die, globalism will win out in the end.The actual crimes committed by the EU against the European peoples are directly in violation of the 1948 UN genocide convention, Article II: (c) Deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part; (d) Imposing measures intended to prevent births within the group; (e) Forcibly transferring children of the group to another group.* The man who does not exercise the first law of nature—that of self preservation — is not worthy of living and breathing the breath of life.

TELEVISION HISTORY IN BRIEF

Television history

At 1928 Baird transmits from London to New York, using his mechanical system.with 30 vertical lines. By 1930 it was clear that mechanical television systems could never produce the picture quality required for commercial success. For this reason mechanical system was rapidly succeeded by the electronic TV systems. The first all-electronic American systems in 1932 used only 120 scanning lines at 24 frames per second Since the mid-1930s picture repetition frequency (field rate or frame rate) has been the same as the mains frequency, either 50 or 60Hz according to the frequency used in each country. This is for two very good reasons. Studio lighting generally uses alternating current lamps and if these were not synchronised with the field frequency, an unwelcome strobe effect could appear on TV pictures. Secondly, in days gone by, the smoothing of power supply circuits in TV receivers was not as good as it is today and ripple superimposed on the DC could cause visual interference. If the picture was locked to the mains frequency, this interference would at least be static on the screen and thus less obtrusive.To determine what electronic system to use, the BBC sponsored trial broadcasts by two systems, one by Baird, with 240 lines, and one by EMI with 405 lines. Scheduled electronic television broadcasting began in England in 1936 using 405-line system (lasted until the 1980s in the UK). Germany made their forst TV broadcasts at 1936 olympics using 180-line TV system. Germany also made their TV broadcasts by the fall of 1937 using a 441-line system. Also fFrance tested TV (455 line system). RCA introduced electronic television to the U. S. at the 1939 World's Fair,and began regularly scheduled broadcasting at the same time (525 line system).In 1940 the USA established its 525-line standard. At year 1941 the 525-line standard, still in use today in USA, was adopted.Russia also produced TV sets before the war (240 and 343 line systems).World War Two interrupted the development of television. Immediately after World War Two production of TV sets started in the U.S-In USA there was TV broadcasts and few throusand receivers at 1945. In the early 1950s, two competing color TV systems emerged: CBS sequential color (used color wheel) and RCA dot sequential system. At 1953 color broadcasting officially arrives in the U.S. on Dec. 17, when FCC approves modified version of an RCA system.It calls this new RCA color system "NTSC" color. The first NTSC color TVs were on the marker at 1954.In Europe the TV broadcasts started to use experiment using 625 line system 1950s. This standard is used nowadays throughout Europe. France also tried 819 line system at the same time (this system was in use to 1980s). The rest of Europe opted for 625 lines, a system devised in 1946 by two German engineers, M??ller and Urtel (it appears that the Russians came up independently with a very similar system). The use of PAL color standard started at around 1967 and is still in use. The SECAM color system (used in France) testing started also at 1967. The TV broadcasting history has not ended. The newst thign is digital television. It is expected that terrestrial television will open up billion-dollar opportunities for those companies and organisations best prepared to embrace this new broadcasting era. At 1996 small digital satellite dishes hit the market. They become the biggest selling electronic item in history next to the VCR.

Using TV 24H

TV has something for everyone. Idiots, intellectuals, fans of all sorts. Some people are couch potatoes, watch anything just to sit there and be mindless. That's their problem. Children have always needed to be monitored by their parents. If people gotta a mind for it they could figure out the real news even without the internet and there has always been a library.

Is TV bad in and of itself? The researchers aren’t saying that. But we all know that watching television is a solitary, isolating occupation that keeps you sedentary. Sitting in front of the boob tube reduces the time you have available to exercise, interact with your family, read books, and be outdoors. This new research dovetails with other studies, which have linked excessive TV time to obesity and higher rates of cardiovascular disease.

watching too much television can jeopardize your whole family’s health.

This should be a wake-up call to all adults. Stay active. Go outside. Spend time with your spouse and your children with the television off. Read a book and do crossword puzzles to stimulate your imagination and your brain. Reduce your screen time as much as you can.

The National Cancer Institute researchers suggest that watching TV is a public health issue. The price we are paying for our technology-driven lives may be much higher than we previously realized !

DON'T WATCH TV AT ALL !!

The Propaganda TV Machine a.k.a. The Ministry of Truth delivers The Truth from The Government to the people.

At least, that's what they say. In fact, a Propaganda Machine is only employed by The Empire and used to brainwash people into Gullible Lemmings who believe that everything is all right when in fact, it isn't, and that the very people who could help them are their enemies.

Girl Looking TV.

Happy Times:

Do you remember when a telly looked like a real telly? When it was a piece of furniture that you lavished love on, even polished from time to time ?When it was a piece of somewhat at looking in to ?When it was a piece of Highest tech looking inside ? First, this site is a Digital free, HD free, flat panel, HDMI, China, Turks, Afrika free zone. All in all a wealth of vintage information at your finger tips, a one stop unique experience. So step on in, leave the modern throw-away world behind, travel back in time to a vintage world of repair and enjoy.This site has stirred memories about the watching TV's days on a CRT TUBE television......Childhood memories, your parents getting their first colour tv, a b/w or color portable, perhaps memories of renting or buying your first set remote featured, perhaps your days working in the trade, selling or repairing them....... If you enjoyed this site, found its content left you all misty eyed then just talk about it as it would be very welcome............like the time to recover and restore a set ................and happy reminiscing.

Digital TV in Brief.

Digital TV:

Digital television is a hot topic now.If you have looked at television sets at any of the big electronics retailers lately, you know that Digital TV, or DTV, is a BIG deal right now in the U.S. In Europe Digital TV is also a hot topic, because many countries have started terrestrial digital TV broadcasts and plan to end analogue broadcasts after some years (will take 5-10 years). Satellite TV broadcasts have also shifted very much to digital broadcasts.The main advantage if digital broadcasts are that it does not havethe picture quality problems of analogue TVs (it had it's own videoproblems caused by video compression), it allowes putting more TV channels to same medium (TV channel frequencies and satellites) and it allows new services (like HDTV and interactive multimedia). The digital brodcasts are generally designed to use such modulation that the digital data stream (typically around 20-30 Mbit/s) is modulated to the same bandwidth (around 6 MHz) as the analogue TV broadcasts. The used modulation vary between different media, which means thatdifferent modulation techniques are used in terrestrial transmissions, cable TV and satellite. Different modulations are used because of the different characteristics of those transmission medias. There is not on "digital TV", but several different variations of it in use.The basic technology of digital TV, known as MPEG 2 video compressionand MPEG 2 transmission stream format, is same around the world, butis is used somewhat differently in different standards used in differentcountries.

USA uses ACTS Digital Televisio Standard, which standardizes NTSC format transmissions, HDTV transmission, sound formats and data signal modulation in use. The ATSC MPEG-2 formats for DTV, including HDTV, uses 4:2:0 samling for video signal. The US system uses a fixed power and a fixed maximum bitrate, at which some bits are always transmitted. That rate is typically 19.3 Mb/sec.

Europe uses DVB (Digital Video Broadcasting) standard. This standardallows basically normal PAL resolution transmisssion (vasically HDTVcould be added later but is not yet standardized) with several audio formats, digital data rates and digital signal modulation. There are several different variations fo DVB standard for different media:

DVB-T for terrestrial broadcastsDVB-S for satelliteDVB-C for cable TV

Those different DVB versions varyon the data signal modulation methods, error correction and frequency bands used. DVB and option for some interactive extra services, but thestandardization of this is not ready here yet(there are fire different incompatible interactive servicessystems in use in different countries and by different broadcasters).

The process of transmitting digital TV signal is the following: Analog video/audio - digitisation - MPEG compression - Multiplexing ( youcan now call it digital) - Preparation for transmisson - modulation toanalog carrier.Reception process is the following: Demodulation of analogue carrier - Error correction - Demultiplexing - MPEG decompression - DA conversion to get analogue signal (unless you use digital display). The analoguie video signal that gets digitized can be practically from any video source, for example produced with old analogue video production equipment and distributed with a video tape. In high-end system the information is analogue only in the image sensor on the video camera, and from this on the signal gets digitally processed. In many real-life TV production systems the reality is something between those two extremes.

At least in Europe, the signal level requirements for DVB-T are well below the analog requirements, so the transmitter power is much less than on the analog side. In the NorDig recommendation the minimum received signal level for 64QAM, 7/8 code rate with a Rayleigh fading path and 8 dB receiver noise figure would be -64 dBm. With other code rates, modulations and fading mechanisms, the requirement is lower. Many receivers can perform much better at conditions where there is no fading (a quasi error free less than one uncorrected error/hour signal even at 27 dBuV (-82 dBm) with 64QAM and 8 MHz channel width). For analog signals, the recommended level is more than 1 mV (+60 dBuV, -49 dBm). While the ERP can be at least 10 dB lower than analog, the question of power consumption is more complicated, since COFDM with 64QAM carriers require a quite good linearity, which may affect the efficiency and hence power consumption.

Digital TV system in use in USA

The FCC mandate to change our broadcast standards from NTSC analog to ATSC digital broadcasting (DTV) is big bold move, requiring changes in everything from the way the studios shoot video, the format that's transmitted, to the equipment we use to receive and watch broadcastsDTV (digital TV) applies to digital broadcasts in general and to the U.S. ATSC standard in specific. The ATSC standard includes both standard-definition (SD) and high-definition (HD) digital formats. The notation H/DTV is often used to specifically refer to high-definition digital TV. The federal mandate grants the public airwaves to the broadcasters to transmit digital TV in exchange for return of the current analog NTSC spectrum, allowing for a transition period in the interim. At the end of this period scheduled for 2006, broadcasters must be fully converted to the 8VSB broadcast standard. Digital Television ("DTV") is a new broadcast technology that will transform television. The technology of DTV will allows TV broadcasts with movie-quality picture and CD- quality sound and a variety of other enhancements (for example data delivery). With digital television, broadcasters will be able to offer free television of higher resolution and better picture quality than now exists under the current mode of TV transmission. If broadcasters so choose, they can offer what has been called "high definition television" or HDTV, television with theater-quality pictures and CD-quality sound. . Alternatively, a broadcaster can offer several different TV programs at the same time, with pictures and sound quality better than is generally available today. HDTV (high-definition TV) encompasses both analog and digital televisions that have a 16:9 aspect ratio and approximately 5 times the resolution of standard TV (double vertical, double horizontal, wider aspect). High definition is generally defined as any video signal that is at least twice the quality of the current 480i (interlaced) analog broadcast signal. There are 18 approved formats for digital TV broadcasts, but only two (720p/1080i) are proper definition of the term HDTV. The advent of high definition has allowed monitors to read images differently, either in standard interlaced format or progressively. Sets that do not have any decoding capabilities but can display the high-resolution image is often labeled as "HD-Ready" a term that describes 80% or more of the Digital TVs on the market. HDTV displays support digital connections such as HDMI (DVI) and IEEE 1394/FireWire, although standardization is not finished. HDTV in the US is part of the ATSC DTV format. The resolution and frame rates of DTV in the US generally correspond to the ATSC recommendations for SD (640x480 and 704x480 at 24p, 30p, 60p, 60i) and HD (1280x720 at 24p, 20p, and 60p; 1920x1080 at 24p, 30p and 60i). In addition, a broadcaster will be able to simultaneously transmit a variety of other information through a data bitstream to both enhance its TV programs and to provide entirely new services. The technical specifications of USA DTV system is defined in ACTS Digital Television Standards.

Digital TV in Europe

Digital TV brodacasting in Europe is done according to DVB standards. DVB technology has become an integral part of global broadcasting, setting the global standard for satellite, cable and terrestrial transmissions and equipment. There are three versions of DVB in use: DVB-S, DVB-C and DVB-T.DVB-T is a flexible system allowing terrestrial broadcastersto choose from a variety of options to suit their various service environments. This allows the choice between fixed roof-top antenna, portableand even mobile reception of DVB-T services. Broadly speaking the trade-off in one of service bit-rate versus signal robustness.

DVB-T network is very flexible. Having many transmitters all on the same frequency is not a problem for the used COFDM based system. COFDM has been chosen and designed to minimise the effects of multipath in obstructed reception areas. In fact multipath signals can significantly improve the overall received signal with no adverse effects. These properties are particularly valuable for radio cameras and mobile links. DVB-T because of its unique design which allows single frequency networks (SFN). This means that many transmitters along the planned routes can transmit on the same frequency. It is also possible to use simple gap fillers that amplify and retransmit the signal. In-air digital TV broadcasts in Europe use DVB-T. 8 MHz of bandwidth may be used to provide a 24 Mbps digital transmission path using Coded Orthogonal Frequency Division Multiplexing (COFDM) modulation (theoretical maximum 31.67 Mbits for 8 MHz bandwidth). In cases where less bandwidth is available (6 or 7 MHz), the data rate is somewhat lower (around 20 Mbit/s).

DVB-C does the same function as DVB-T, but the modulation used in this system is optimized to operate well in cable TV networks. The modulation used in DVB-C is QAM. Systems from 16-QAM up to 256-QAM can be used, but the system centres on 64-QAM, in which an 8MHz channel can accommodate a physical payload of about 38 Mbit/s. Digital cable TV in Europe uses DVB-C. The DVB standard for the cable return path has been developed jointly with DAVIC, the Digital Audio Visual Council. The specification uses Quadrature Phase Shift Keying (QPSK) modulation in a 200kHz, 1MHz or 2MHz channel to provide a return path for interactive services (from the user to the service provider) of up to about 3Mbit/s. The path to the user may be either in-band (embedded in the MPEG-2 Transport Stream in the DVB-C channel) or out-of-band (on a separate 1 or 2MHz frequency band).

DVB-S is the satellite version of DVB. Satellite transmission has lead the way in delivering digital TV to viewers. Established in 1995, the satellite standard DVB-S is the oldest DVB standard, used on all six major continents. QPSK modulation system is used, with channel coding optimised to the error characteristics of the channel. A typical satellite channel has 36 MHz bandwidth, which may support transmission at up to 38 Mbps (assuming delivery to a 0.5m receiving antenna) using Quadrature Phase Shift Keying (QPSK) modulation. 16 bytes of Reed Solomon (RS) coding are added to each 188 byte transport packet to provide Forward Error Correction (FEC) using a RS(204,188,8) code. For the satellite transmission, the resultant bit stream is then interleaved and convolutional coding is applied.

The core of the DVB digital data stream isthe standard MPEG-2 "data container",which holds the broadcast and service information.This flexible "carry-all" can containanything that can be digitised, includingmultimedia data. The MPEG-2 standards define how to format the various component parts of a multimedia programme (which may consist of: MPEG-2 compressed video, compressed audio, control data and/or user data). It also defines how these components are combined into a single synchronous transmission bit stream. The process of combining the steams is known as multiplexing. The multiplexed stream may be transmitted over a variety of links, standards / products.Each MPEG-2 MPTS multiplex carries a number of streams which in combination deliver the required services. A typical data rate of such multiplex is around 24 Mbps for terrestrial brodcasts.

European DVB systems currently transmit only standard definition TV signals and set top boxes also handle only normal TV resolution. It would be possible to transmit HDTV signals on DVB data stream, but those broadcasts have not yet started in any wide scale. There is one satellite broadcater that broadcasts HDTV DVB signals in Europe (some cable TV operators carry that signal on their cable).

Many DVB-T integrated TV sets, and some set top boxes, in the Europe come with a Common Interface slot - which is pretty much the same form-factor as a PC Card (aka PCMCIA) used in PC laptops. This CI slot accepts a Conditional Access Module, in the same way that DVB-S receivers do, which implements at least one (some can do more than one) decryption algorithm. This CAM may also, itself, have a smart card slot to accept a consumer subscription card to authorise decryption - you plug your smartcard into your CAM and your CAM into the CI slot in your receiver/IDTV. Some DVB receivers have an integrated CAM (in the case of some receivers this is implemented purely in software, with no extra hardware required) rather than a CI slot to plug in a 3rd party device. With these type of receivers you just plug in the smart card and don't have to worry about CI slots and buying CAMs. So there is an interface standard for DVB - but different broadcasters can chose different encryption schemes, requiring different CAMs for decryption.

DVB Standards and related documents are published by the European Telecommunications Standards Institute (ETSI). These include a large number of standards and technical notes to complement the MPEG-2 standards defined by the ISO.

There are few different standard how interactive TV functionaly is implemented in DVB-systems in use in differenct countries. DVB-MHP is one gaining some acceptance. Multimedia Home Platform (MHP) is the open middleware system designed by the DVB Project (www.dvb.org).

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